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A base-mediated carbocyclization study has been performed between two allowed Baldwin cyclization modes (6-exo-trig and 6-exo-dig) and it was found that 6-exo-trig cyclization was preferred over 6-exo-dig. Allyl cyanide was found to be suitable and efficient pronucleophile for this investigation and two sp2–sp2 transition-metal-free C−C bond formations took place in a single operation to yield two differently functionalized biaryl compounds.

A concise and efficient base-induced synthesis of stair-shaped, 4-methylthio-2-oxo-5,6-dihydro-2H-naphtho[1,2-b]pyran[2,3-d]oxepine-3-carbonitriles () has been delineated by the reaction of 3,4-dihydronaphtho[1,2-b]oxepin-5(2H)-one () and methyl 2-cyano-3,3-dimethylthioacrylate in DMSO using powdered KOH as a base at room temperature. Amination of has been achieved by reaction with secondary amine in ethanol at reflux temperature to yield 4-sec-amino-2-oxo-5,6-dihydro-2H-naphtho[1,2-b]pyran[2,3-d]oxepine-3-carbonitriles (). Reaction of with aryl methyl ketone () in DMSO at room temperature using powdered KOH as a base produced stair-shaped 5-aryl-7,8-dihydro-1,4-dioxa-2,3-dioxodinaphtho[1,2-b,d]oxepine () in good yields. However, reaction of 6-aryl-2H-pyran-2-one-3-carbonitrile () with 3,4-dihydronaphtho[1,2-b]oxepin-5(2H)-one () did not give similar product, but in lieu 4-aryl-5,6-dihydronaphtho[1,2-b]oxepino[4,5-b]pyran-2-ylidene)acetonitrile () was isolated and characterized.

This chapter is entirely devoted on the nomenclature of various monocyclic, bicyclic, tricyclic, and polycyclic, including ortho-fused, ortho-peri-fused, bridged, and spiro, heterocycles with one or more similar or dissimilar heteroatoms present in the cyclic system. In heterocyclic chemistry every heterocyclic system has a special name, while individual compounds are named also by a trivial name based on their origin of occurrence or on their special properties. Hantzsch and Widman introduced methods for naming the five- and six-membered heterocycles, which later on extended to saturated, unsaturated, and other ring sizes of heterocyclic compounds. In this system an appropriate prefix is used for heteroatoms and their ring size. The stem ol (ole) has been used in the case of five-membered heterocycles, while the in (ine) stem is used for six-membered heterocycles. Difficulties arose in naming some ortho or ortho-peri-fused, bridged, and spiro heterocyclic ring systems by the Hantsch-Widman nomenclature, and a set of rules were framed for systematic names of such heterocycles by the International Union of Pure and Applied Chemistry, which is used most frequently worldwide. Replacement nomenclature, also known as “a” nomenclature, has been used to name the heterocyclic compounds in which prefixes end with “a” and the position and prefix for each heteroatom precede the name of corresponding hydrocarbons.

A computational approach has been attempted for the screening of 4-pyridoxinium (4P) ring based reactivators for paraoxon inhibited AChE. The oxime molecules were designed with the common 4P skeleton and varying the carbon linkers. Initially, the AChE binding capability was assessed by molecular docking with PDB:2WHP and 3ZLV, which showed important interactions with Ser298, Try124 and Trp286. These computational results were validated by an in vitro AChE binding assay, which showed binding affinities in the range of 10–90%. Finally, reactivation potency was calculated as % reactivation on paraoxon inhibited eelAChE in the concentration range of 10−5 to 10−7 M. It was observed that introduction of an aliphatic linker attached to 4-pyridoxime has a high binding affinity and hence, may act as a good reactivator as compared to the aromatic pyridoximes.

We have reported a simple, unprecedented base promoted synthesis of 7-substituted-1-(2-cyano-phenyl/phenyl)-3-sec amino-4,5-dihydro-1H-benz[e]indene-1,2-dicarbonitriles by reaction of 2-oxo-4-sec amino-5,6-dihydro-2H-benzo[h]chromene-3-carbonitriles and 2-cyanomethyl-benzonitrile/phenyl-acetonitrile under basic conditions at 100 °C. This reaction involves ring opening of 2-oxo-4-sec amino-5,6-dihydro-2H-benzo[h]chromene-3-carbonitrile by a carbanion generated in situ from 2-cyanomethylbenzonitrile/phenyl-acetonitrile followed by oxidative cyclization to afford the desired product. Alternatively, reaction of 6-aryl-4-sec amino-2H-pyran-2-one-3-carbonitriles and 2-cyanomethyl-benzonitrile under basic conditions provides functionalized benzo[h]quinolines. The structure of the synthesized compound was confirmed by single crystal X-ray.

An efficient regioselective synthesis of polycyclic diheteroaryl[b,d]pyrans and diheteroaryl[c,e][1,2]diazepines has been reported through ring transformation reactions of 2-oxo-2,5-dihydrothiochromeno[4,3-b]pyrans (3,4), 2-oxo-5,6-dihydro-2H-benzo[b]pyrano[2,3-d]oxepine/thiepine (8, 9) and 6-oxo-3,6-dihydro-2H-naphtho[1,2-b]pyrano[2,3-d]oxepine (15) by hydrazine, at ambient and reflux temperature. Nine compounds viz 5a,b; 10a,c,d; 12b; 13b; 16 and 1-methylthio-5,6-dihydrobenzo[f]quinoline (0.1–100 μM) were screened for their cytotoxicity in normal (IEC-6), carcinoma (Colo-205) and HepG2 cell lines. None of the compounds showed cytotoxicity in normal IEC-6 cells while 10a,d and 16 resulted in killing of Colo-205 cells with IC50 ranging 20–60 μM while 10c and 13b caused killing of HepG2 cells with IC50 values ranging 60–80 μM concentration. Further, 10a,d and 16 caused apoptosis through a cascade of mitochondrial pathway in Colo-205 cells indicating anticancerous potential against intestinal cancer. Interestingly, compounds 10c and 13b exhibited apoptosis through mitochondrial pathway in HepG2 cells suggesting anticancer activity against hepatic cancer.

An expeditious, metal free, simple and convenient synthesis of partially reduced thia[5]helicenes and oxa-thia[5]helicenes, appended with nitrile and amino functionalities such as 3-sec.amino-5,6-dihydro-2H-1-thia-dibenzo[c,g]phenanthrene-4-carbonitriles 7 and (Z)-2-(5,6-dihydrobenzo[f]thiochromeno[3,4-c]-3-(2H)-ylidene)acetonitriles 6 has been delineated through base-catalyzed ring transformation of 4-sec.amino-2-oxo-2,5-dihydrothiochromeno[4,3-b]pyran-3-carbonitriles 4 by 2-tetralones 5. The molecular structure of one of the partially reduced thia[5]helicenes has been determined by X-ray crystallographic analysis. In order to calculate the inversion barrier of the helimeric enantiomers P-7a and M-7a, the molecular geometries of both, the ground states and the transition states have been optimized by the density functional theory (DFT) using B3LYP/6-311G.** Based on these structures, helimerization barrier of 44.36 K cal mol−1 has been predicted using MP2/6-311G** single-point energy calculations.

In order to understand how electronic and other structural characteristics of biphenyl phosphine ligands affect Pd-catalyzed C-N and C-C bond-forming reactions, a new ligand, 2-(dicyclohexylphosphino)-4'-(N,N-dimethylamino)-1,1'-biphenyl, was synthesized. This compound is isomeric with the commercially available 2-(dicyclohexylphosphino)-2'-(N,N-dimethylamino)-1,1'-biphenyl that has been useful in C-N bond-forming reactions of nucleosides. The new p-dimethylamino biphenyl ligand bears electronic similarities to the o-dimethylamino isomer, but it also possesses structural similarities to 2-(dicyclohexylphosphino)biphenyl, such as the unsubstituted ortho positions in the non-phosphine ring. Whereas 2-(dicyclohexylphosphino)biphenyl can support catalysts for C-C bond formation, it was not effective in promoting aryl amination of a nucleoside substrate. However, the new ligand proved to be effective in promoting both aryl amination and C-C bond-forming reactions of nucleoside substrates, with some reactions even occurring at room temperature. Thus, the composite structural elements of this new ligand are thought to be criteria for reactivity of the catalytic system derived from it. We have probed the structures of the isomeric N,N-dimethylamino biphenyl ligands by X-ray crystallographic analysis. Interactions of the two ligands with Pd(OAc)(2) have been investigated by (31)P NMR, and they show substantial stoichiometry-dependent differences. These results have been compared to the interactions of Pd(OAc)(2) with 2-(dicyclohexylphosphino)biphenyl as well as 2-(di-tert-butylphosphino)biphenyl, and they reveal marked differences as well. In this process, three cyclopalladated biaryl derivatives have been isolated and characterized by X-ray analysis.

A novel approach to the synthesis of partially reduced different ring sizes of PAH analogs with sec.amino and nitrile functionalities is delineated through base-induced ring transformation of 4-sec.amino-2-oxo-5,6-dihydro-2H-benzo[h]chromene-3-carbonitriles by a carbanion, generated in situ from cyclopentanone, cyclohexanone, cycloheptanone, and cyclooctanone separately in good yields. An increase in the size of cycloalkanone ring beyond cyclooctanone restricts the ring transformation under analogous reaction conditions possibly due to bulky conformation of higher homologs. The synthetic method provides an efficient general route for the construction of angularly fused partially reduced polycyclic aromatic hydrocarbons: 5-sec.amino-2,3,6,7-tetrahydro-1H-cyclopenta[c]phenanthrene-4-carbonitriles, 6-sec.amino-2,3,4,7,8-pentahydro-1H-benzo[c]phenanthrene-5-carbonitriles, 7-sec.amino-2,3,4,5,8,9-hexahydro-1H-cyclohepta[c]phenanthrene-6-carbonitriles, and 8-sec.amino-2,3,4,5,6,9,10-heptahydro-1H-cycloocta[c]phenanthrene-7-carbonitriles.

An efficient regioselective synthesis of pyronyl pendant ethyl methylthiocarbonylalkanoates 5 has been delineated from the base catalyzed reaction of suitably functionalized 2-pyranone 1 and 2-carbethoxycycloalkanones 2 , 6 through successive substitution and regioselective ring opening by in situ generated mercaptide ion. To assess the effect of C-4 substituent on regioselectivity, reactions of 6-aryl-3-cyano-4-(piperidin-1-yl)-2-oxopyran 8 with 2-carbethoxycyclohexanone 6a and 2-carbethoxy-2-methylcyclohexanone 6b were carried out separately under analogous reaction conditions but the compounds isolated were identical and characterized as 4-aryl-8-methyl-2-piperidin-1-yl-5,6,7,8-tetrahydronaphthalene-1-carbonitriles 9 . Ethyl 2-(5-amino-4′-bromo-4,6-dicyanobiphenyl-3-yl)-5-methylsulfanylcarbonylpentanoate 10 has also been prepared through base catalyzed ring transformation of ethyl 2-[6-(4-bromophenyl)-3-cyano-2-oxo-2 H -pyran-4-yl]-5-methylsulfanylcarbonylpentanoate 5d by malononitrile in DMF.

A facile and short synthesis of 2-oxo-4-sec-amino-2,3,5,6-tetrahydrobenzo[f]isoquinoline-1-carbonitriles has been delineated through base catalyzed ring transformation of 5,6-dihydro-2-oxo-4-sec-amino-2H-benzo[h]chromene-3-carbonitrile by cyanoacetamide in excellent yields.

A novel and efficient regioselective synthesis of various arylated highly congested 7-aryl-5-methylsulfanylindan-4-carbonitriles (3a–f), methyl 7-aryl-5-methylsulfanylindan-4-carboxylates (10a–e) and 7-aryl-5-methylsulfanylindan-4-carboxylic acids (11a–e) through base-catalyzed reaction of 6-aryl-4-methylsulfanyl-2-oxo-2H-pyran-3-carbonitriles (1a–f) and methyl 6-aryl-4-methylsulfanyl-2-oxo-2H-pyran-3-carboxylates (9a–e) by cyclopentanone (2) has been delineated. The synthetic potential of 2-pyranone was explored further to generate molecular diversity using 6-aryl-4-sec-amino-2-oxo-2H-pyran-3-carbonitriles (7a–h), 5,6-diaryl-4-methylsulfanyl-2-oxo-2H-pyran-3-carbonitriles (5a,b) and methyl 5,6-diaryl-4-methylsulfanyl-2-oxo-2H-pyran-3-carboxylates (12a,b) as precursors for the ring transformation by cyclopentanone to assess the effects of substituents on the course of the reaction to obtain highly congested indans, 6,7-diaryl-5-methylsulfanylindan-4-carbonitriles (6a,b), 7-aryl-5-(piperidin-1-yl)indan-4-carbonitriles (8a–h) and methyl 6,7-diaryl-5-methylsulfanylindan-4-carboxylates (13a,b).

An efficient and concise synthesis of 7- sec -amino-5,13-dihydro-6 H -indeno[1,2- c ]phenanthrene-8-carbonitriles is described through base catalyzed ring transformation of 4- sec -amino-2-oxo-5,6-dihydro-2 H -benzo[ h ]chromene-3-carbonitriles with 1-indanone in moderate to good yields.

A concise synthesis of highly functionalized 5,6-dihydrobenzo[h]quinoline-3-carbonitriles is delineated through base induced ring transformation of 4-sec-amino-2-oxo-5,6-dihydro-2H-benzo[h]chromene-3-carbonitriles with S-methylisothiourea sulfate and 1-carboxamidinepyrazole hydrochloride, separately, in DMF. Under analogous reaction conditions the ring transformation of 4-sec-amino-2-oxo-5,6-dihydro-2H-benzo[h]chromene-3-carbonitriles by formamidine acetate provided 4-sec-amino-benzo[h]quinoline-3-carbonitriles in moderate yields, while with benzamidine hydrochloride, the reaction followed the same mechanism to yield 2-phenyl-4-sec-amino-5,6-dihydrobenzo[h]quinoline-3-carbonitriles.

An innovative synthesis of aryl tethered 1,3-dimethylimidazo[4,5-b]pyrazin-2-ones 4 and 6 has been delineated through base catalyzed ring transformation of 6-aryl-4-(piperidin-1-yl)-2H-pyran-2-one-3-carbonitriles 1 and methyl 6-aryl-4-methylsulfanyl-2H-pyran-2-one-3-carboxylates 5 with 7-acetyl-1,3-dimethyllumazine 2 with subsequent ring contraction of the fused pyrimidine to an imidazole ring. An additional product, methyl [6-(1,3-dimethyl-2-oxo-2,3-dihydro-1H-imidazo[4,5-b]pyrazin-5-yl)-4-thiophen-2-ylpyran-2-ylidene]acetate 8b, was also isolated from the reaction of 5 and 2, as a minor constituent.

Substituent-controlled regioselective synthesis of highly functionalized 1,2-teraryls 3a – k has been achieved through ring transformation of 6-aryl-4-(pyrrolidin-1-yl/piperidin-1-yl)-2 H -pyran-2-one-3-carbonitriles 1a – g by aryl acetones 2a – c in the presence of powdered KOH in DMF in very good yield. Under similar reaction conditions, 6-aryl-4-methylsulfanyl-2 H -pyran-2-ones 5a – f afforded 1,7-diaryl-2-methyl-4 H ,5 H -pyrano[3,4- c ]pyran-4,5-diones 6a – j as major products and 3,4-diaryl-2-methyl-6-methylsulfanylbenzonitriles as minor constituents 7a – j .

A novel synthesis of highly functionalized alkylsulfanylmethyl arenes 8a–m through the ring transformation of 6-aryl-4-methyl/ethylsulfanyl-2H-pyran-2-one-3-carbonitriles 1a–j, by reaction with methyl vinyl ketone 2, is delineated and illustrated. To ascertain the course of reaction, 3-arylsulfanylmethyl-2-methyl-6-methylsulfanyl-4-phenylbenzonitriles 8k–m were also prepared from the reaction of 1 with 4-arylsulfanyl-butan-2-ones 7c,d.

Various 6-aryl-4-substituted-2H-pyran-2-one-3-carbonitriles (1a-d) have been synthesized as precursor for the synthesis of 3,4-dihydro-1H-isothiochroman (2a) and benzocycloalkanes (2b-e). Highly functionalized 9-thiaphenanthrene (3b) and phenanthrene (3a) have also been obtained from the reaction of 1c with thiochroman-4-one and 1-tetralone separately. Similarly 4 has been obtained by the ring transformation of 1d by 4-trifluoromethylacetophenone. Most of the synthesized compounds were evaluated for alpha-glucosidase and protein tyrosine phosphatase inhibitory activities. Some of the compounds, 2a, 3a and b and 4 displayed better alpha-glucosidase inhibitory activity compared to standard drug acarbose.

A new precursor 2-(1-cyano-2,2-bis(methylthio)vinyl)benzonitrile has been synthesized by the reaction of 2-cyanomethylbenzonitrile, carbon disulfide and methyl iodide under basic conditions. The reaction of 2-(1-cyano-2,2-bis(methylthio)vinyl)benzonitrile with various functionalized aryl/heteroaryl methyl ketones or acetone under basic conditions afforded 4-amino-3-aroyl/heteroaroyl/acetyl-2-methylsulfanylnaphthalene-1-carbonitriles in good yields through a (5C + 1C) annulation strategy; this involves sequential intermolecular, followed by intramolecular, C–C bond formation reactions. The structure of the product was confirmed by single crystal X-ray crystallography.

A novel transitional metal ligand derivatized from EDTA-conjugated 2-amino-4-methyl pyridine, an acyclic vehicle (EDTA-Mepy2 ) was designed, synthesized, and characterized for PET imaging with ⁶⁸Ga. The drug likeliness and appropriate lipophilicity were first analyzed by molecular docking studies which shows interactive property of ligand with serum albumin protein (HSA: PDB 1E78), at Lys199, Arg257, and His242 residues, which make it more appropriate in transportation as a specific ligand for PET imaging. As a confirmation, binding constant of the ligand with human serum albumin was calculated at λex = 350 nm which was found to be 4.9 × 10³ m⁻¹. The pharmacokinetics of (68) Ga-EDTA-Mepy2 was analyzed by blood kinetics (t(1/2) slow: 3 h 56 min and t(1/2) fast: 32 min) and biodistribution (maximum % ID/g was found in kidney at 1 h). Further the capability of this ligand was analyzed as optical marker also, by recording λex = 380 nm, RFU = 8000; 710 nm, RFU = 1000 units at fixed λem = 280 nm. Additionally, in physiological conditions where its stability was calculated, suggests 15-20 times selectivity over the endogenously present metal ions (KG aL /KZ nL = 14.3, KG aL /KC uL = 18.1).

An efficient and concise de novo synthesis of ferrocenyl tethered partially reduced phenanthrenes is described through base-catalyzed ring transformation of 4-sec-amino-2-oxo-5,6-dihydro-2H-benzo[h]chromene-3-carbonitriles with acetylferrocene.

An easy and efficient synthesis of phenanthrene derivatives through base catalyzed ring transformation of 4-sec-amino-2-oxo-5,6-dihydro-2H-benzo[h]chromene-3-carbonitriles with acetyltrimethylsilane is described in good yields. The advantage of this reaction is the direct transformation of 2-oxobenzo[h]chromene into phenanthrene via C–C insertion from acetyltrimethylsilane.

The one-pot substituent-directed regioselective synthesis of 1,7-diaryl-2-methyl-4H,5H-pyrano[3,4-c]pyran-4,5-diones 3 as the major and 3,4-diaryl-2-methyl-6-methylsulfanylbenzonitriles 4 as the minor products has been delineated through ring transformation of suitably functionalized 2H-pyran-2-ones 1 with aryl acetones 2 . Under similar reaction conditions, 6-aryl-4-sec-amino-2H-pyran-2-ones 5 led, regioselectively, to 3,4-diaryl-2-methyl-6-sec-aminobenzonitriles 6 .

A series of 5-[(5-aryl-1 H -pyrazol-3-yl)methyl]-1 H -tetrazoles 3a – h have been synthesized and evaluated for their in vivo antihyperglycemic activity. Some of the synthesized compounds have shown significant glucose lowering activity in male Sprague–Dawley rats in sucrose loaded model. These compounds were also evaluated for their peroxisome proliferator activated receptor γ agonistic property, but none of them displayed any significant activity.

The synthesis of three new classes of heteroarenes, built through the sequential fusion of naphthalene, benzo/naphtho[b]oxepine and thiochromene rings with pyran and pyrimidine ring systems to give 'U and Z' shaped structural frameworks is reported. The methodology is based on the synthesis of pyran fused intermediates, 1-methylthio-3-oxo-5,6-dihydro-3H-benzo[f]chromene-2-carbonitrile (3), 4-methylthio-2-oxo-5,6-dihydro-2H-benzo/naphtho[b]pyrano[2,3-d]oxepine-3-carbonitriles (10, 20) and 4-methylthio-2-oxo-2,5-dihydrothiochromeno[4,3-b]pyran-3-carbonitriles (15) from the reaction of 2-tetralone, benzo/naphtho[b]oxepin-5-ones and thiochromen-4-ones with methyl 2-cyano-3,3-dimethylthioacrylate respectively. Further condensation of intermediates 3, 10, 20 and 15 with amidines led to the formation of tetracyclic 'U' shaped 4-amino-2-aryl-7,8-dihydro-5-oxo-5H-naphtho[2,1-b]pyrimido[4,5-d]pyrans (8) and 'Z' shaped 4-amino-2-aryl-5-oxo-12,13-dihydro-5H-benzo/naphtho[b]oxepino[5,4-b]pyrimido[4,5-d]pyrans (12, 22) and 4-amino-2-aryl-5-oxo-5,12-dihydrothiochromeno[4,3-b]pyrimido[4,5-d]pyrans (17). Compound 12f forms a chain of dimers through N-HO interactions as indicated by the X-ray structure analysis, and the quantum chemical calculations performed at the MP2 level indicate that this interaction energy is 10 kJ mol(-1).

The title compounds are obtained through base-catalyzed ring transformation of nitriles (I) by a carbanion, generated in situ from piperidones (II).

A concise and convenient synthesis of various partially reduced 6-sec-amino-1,2,3,4,7,8-hexahydro-, 6-sec-amino-1,2,7,8-tetrahydrobenzo[c]phenanthrene-5-carbonitriles, 6-sec-amino-3,4,7,8-tetrahydro-1H-benzo[c]phenanthrene-2-one-5-carbonitrile cycloalkene ketals, pendant with electron donor and acceptor substituents has been described through base catalyzed ring transformation of 2-oxo-4-sec-amino-5,6-dihydro-2H-benzo[h]chromene-3-carbonitriles by cyclohexanone, 2-cyclohexen-1-one, 1,4-cyclohexanedione monocycloalkene ketals. The acid catalyzed deketalation of 6-sec-amino-3,4,7,8-tetrahydro-1H-benzo[c]phenanthrene-2-one-carbonitrile ketals led to yield 6-sec-amino-3,4,7,8-tetrahydro-1H-benzo[c]phenanthrene-3-carbonitrile-2-ones in excellent yield. We also performed the X-ray studies of the molecules 3d and 6a to know the degree of non-planarity.

A novel approach to the synthesis of partially reduced different ring sizes of PAH analogs with sec.amino and nitrile functionalities is delineated through base-induced ring transformation of 4-sec.amino-2-oxo-5,6-dihydro-2H-benzo[h]chromene-3-carbonitriles by a carbanion, generated in situ from cyclopentanone, cyclohexanone, cycloheptanone, and cyclooctanone separately in good yields. An increase in the size of cycloalkanone ring beyond cyclooctanone restricts the ring transformation under analogous reaction conditions possibly due to bulky conformation of higher homologs. The synthetic method provides an efficient general route for the construction of angularly fused partially reduced polycyclic aromatic hydrocarbons: 5-sec.amino-2,3,6,7-tetrahydro-1H-cyclopenta[c]phenanthrene-4-carbonitriles, 6-sec.amino-2,3,4,7,8-pentahydro-1H-benzo[c]phenanthrene-5-carbonitriles, 7-sec.amino-2,3,4,5,8,9-hexahydro-1H-cyclohepta[c]phenanthrene-6-carbonitriles, and 8-sec.amino-2,3,4,5,6,9,10-heptahydro-1H-cycloocta[c]phenanthrene-7-carbonitriles.

An efficient and convenient synthesis of 2-oxa- and 2-thia-3,4,7,8-tetrahydro-1H-benzo[c]phenanthrenes has been described through base-induced ring transformation of 2-oxo-4-sec.amino-5,6-dihydro-2H-benzo[h]chromene-3-carbonitriles by 4-oxotetrahydropyran and 4-oxotetrahydrothiopyran, respectively, in excellent yields.

A facile and short synthesis of 2-oxo-4-sec-amino-2,3,5,6-tetrahydrobenzo[f]isoquinoline-1-carbonitriles has been delineated through base catalyzed ring transformation of 5,6-dihydro-2-oxo-4-sec-amino-2H-benzo[h]chromene-3-carbonitrile by cyanoacetamide in excellent yields.

A novel and efficient regioselective synthesis of various arylated highly congested 7-aryl-5-methylsulfanylindan-4-carbonitriles (3a–f), methyl 7-aryl-5-methylsulfanylindan-4-carboxylates (10a–e) and 7-aryl-5-methylsulfanylindan-4-carboxylic acids (11a–e) through base-catalyzed reaction of 6-aryl-4-methylsulfanyl-2-oxo-2H-pyran-3-carbonitriles (1a–f) and methyl 6-aryl-4-methylsulfanyl-2-oxo-2H-pyran-3-carboxylates (9a–e) by cyclopentanone (2) has been delineated. The synthetic potential of 2-pyranone was explored further to generate molecular diversity using 6-aryl-4-sec-amino-2-oxo-2H-pyran-3-carbonitriles (7a–h), 5,6-diaryl-4-methylsulfanyl-2-oxo-2H-pyran-3-carbonitriles (5a,b) and methyl 5,6-diaryl-4-methylsulfanyl-2-oxo-2H-pyran-3-carboxylates (12a,b) as precursors for the ring transformation by cyclopentanone to assess the effects of substituents on the course of the reaction to obtain highly congested indans, 6,7-diaryl-5-methylsulfanylindan-4-carbonitriles (6a,b), 7-aryl-5-(piperidin-1-yl)indan-4-carbonitriles (8a–h) and methyl 6,7-diaryl-5-methylsulfanylindan-4-carboxylates (13a,b).

An efficient and novel approach to the synthesis of highly congested 3-alkyl-, 4-alkyl-, 3-aryl-, 3,4-dialkyl-, 4-alkyl-3-aryl-, and 3,4-diaryl-9,10-dihydro-1-sec-aminophenanthrene-2-carbonitriles has been delineated through the base-catalyzed ring transformation of 5,6-dihydro-2-oxo-4-sec-amino-2H-benzo[h]chromene-3-carbonitrile by carbanion derived in situ from various ketones in moderate to good yields. 9,10-Dihydrophenanthrenes with and without substituent in the bay region are efficiently and regioselectively synthesized by using propanal and acetyltrimethylsilane as a source of carbanion. Even the synthesis of bisphenanthrenes has been achieved by the ring transformation of 5,6-dihydro-2-oxo-4-sec-amino-2H-benzo[h]chromene-3-carbonitrile by 2-acetylphenanthrene in moderate yield. Highly substituted 3-amino-1-sec-amino-5,6-dihydrophenanthrene-2,4-dicarbonitriles have also been prepared from the reaction of 2-oxobenzo[h]chromene and malononitrile.

An easy and efficient synthesis of phenanthrene derivatives through base catalyzed ring transformation of 4-sec-amino-2-oxo-5,6-dihydro-2H-benzo[h]chromene-3-carbonitriles with acetyltrimethylsilane is described in good yields. The advantage of this reaction is the direct transformation of 2-oxobenzo[h]chromene into phenanthrene via C–C insertion from acetyltrimethylsilane.

An efficient and short synthesis of (5,6-dihydrobenzo[h]pyrido[2,1-b]quinazolin-2-ylidene)acetonitriles, (5,6-dihydrobenzo[h]pyrazino[2,1-b]quinazolin-2-ylidene)acetonitriles and (5,6-dihydrobenzimidazo[1,2-b]benzo[f]isoquinolin-7-yl)acetonitriles in good yields is delineated through base catalyzed ring transformation of 4-(piperidin-1-yl)-2-oxo-5,6-dihydro-2H-benzo[h]chromene-3-carbonitriles with 2-amino-pyridine, 2-aminopyrazine and (imidazo-2-yl)acetonitrile.

An elegant approach to the synthesis of 2,3,6,7-tetrahydrophenanthro[4,3-b]thiophenes has been described through base catalyzed ring transformation of 4-sec-amino-2-oxo-5,6-dihydro-2H-benzo[h]chromene-3-carbonitriles with tetrahydrothiophen-3-one in very good yields.

An efficient and novel approach to the synthesis of highly congested 3-alkyl-, 4-alkyl-, 3-aryl-, 3,4-dialkyl-, 4-alkyl-3-aryl-, and 3,4-diaryl-9,10-dihydro-1-sec-aminophenanthrene-2-carbonitriles has been delineated through the base-catalyzed ring transformation of 5,6-dihydro-2-oxo-4-sec-amino-2H-benzo[h]chromene-3-carbonitrile by carbanion derived in situ from various ketones in moderate to good yields. 9,10-Dihydrophenanthrenes with and without substituent in the bay region are efficiently and regioselectively synthesized by using propanal and acetyltrimethylsilane as a source of carbanion. Even the synthesis of bisphenanthrenes has been achieved by the ring transformation of 5,6-dihydro-2-oxo-4-sec-amino-2H-benzo[h]chromene-3-carbonitrile by 2-acetylphenanthrene in moderate yield. Highly substituted 3-amino-1-sec-amino-5,6-dihydrophenanthrene-2,4-dicarbonitriles have also been prepared from the reaction of 2-oxobenzo[h]chromene and malononitrile.

An innovative and concise synthesis of (7,8-dihydro-5-oxabenzo[c]chrysene-6-ylidene)acetonitriles is described through base catalyzed ring transformation of 2-oxo-4-piperidin-1-yl-5,6-dihydro-2H-benzo[h]chromene-3-carbonitriles with 1-tetralone in very good yields.

A series of ( E )-(2-arylpyrazino[1,2- a ]pyrimidine-4-ylidene)acetonitriles 5a – j and aryl/heteroaryl tethered pyrimidin-4-yl acetonitriles 6a – e has been synthesized in excellent yields through base catalyzed ring transformation of suitably functionalized 2 H -pyran-2-ones 3 using 2-aminopyrazine 4a and arylamidinium salts 4b , separately.

A regioselective synthesis of sterically hindered ethyl arylacetates in one step through ring transformation of suitably functionalized 6-aryl-3,4-disubstituted-2H-pyran-2-ones with ethyl levulinate at room temperature in excellent yields is described.

Various 6-aryl-3-cyano/methoxycarbonyl-4-methylsulfanyl-2H-pyran-2-ones have been synthesized as a potential substitute of 2,4-thiazolidinedione head group to express potent PPAR-γ transactivation response. Some of the screened compounds have shown promising PPAR-γ agonistic activity.

A one-pot synthesis of benzocyclobutane (3a-n) has been developed through base-induced ring transformation reactions of 6-aryl-4-substituted-2H-pyran-2-one-3-carbonitriles (1a-c) and methyl 6-aryl-4-methylsulfanyl-2H-pyran-2-one-3-carboxylate (1d) by cyclobutanone.

A one-pot synthesis of benzocyclobutane (3a-n) has been developed through base-induced ring transformation reactions of 6-aryl-4-substituted-2H-pyran-2-one-3-carbonitriles (1a-c) and methyl 6-aryl-4-methylsulfanyl-2H-pyran-2-one-3-carboxylate (1d) by cyclobutanone.

An unique approach to the synthesis of heterocyclic spiranes through ring switching transformation of suitably functionalized 2H-pyran-2-ones, benzo[h]chromene and thiochromeno[4,3-b]pyrans has been developed. The spirane dimer 11d displayed interesting halogen-hydrogen bonding to generate an elliptical cavity and may be relevant to the generation of a host guest assembly for specific cations and also a low helimerization energy barrier of spirane 17a.

An efficient de novo synthesis of partially reduced naphtho[2,1-h]isoquinolines has been developed through base catalyzed ring transformation of 2-oxo-4-sec-amino-5,6-dihydro-2H-benzo[h]chromene-3-carbonitriles by a carbanion, generated in situ from 1-substituted-4-piperidones in DMF and powdered KOH, in excellent yields. The effect of nitrogen insertion in the D ring of partially reduced benzo[c]phenanthrene on conformational changes has also been studied by X-ray diffraction analysis.