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A cationic palladium-catalyzed arylalkenylation of ynamides is presented. The putative keteniminium arylpalladium intermediate likely dictates the regioselective carbopalladation of the ynamide to form a vinylpalladium species. The capture of this complex by the olefin yields linear conjugated β-alkenyl aminodienes (especially with

A straightforward and sustainable approach for the 1,2-addition of propiolic acids to ynamide has led to bench-stable sp2 (E)-enol-enamides of enediynes and dienynes.

This feature article uncovers a tactical blueprint for the sustainable development of synthetic manifestations in the transition-metal catalyzed directing group assisted multiple annulations (L-type, Y-type, and B-type) of inert C(arene)–H bonds.

A Pd-catalyzed syn-1,2-arylmethylation of internal alkynes (ynamides/ yne-acetates) is described. The readily available and bench stable coupling partners iodo-arenes, and methyl boronic acid are successfully being used to access the methyl containing tetra substituted olefins; notably, the transformation is regio as well stereoselective. The scope is broad (52 examples), showing excellent functional-group tolerance. Finally, synthetic manifestations of the products were also demonstrated.

A straightforward regioselective intramolecular 6

Ynamide, a unique species with inherited polarization of nitrogen lone pair electron to triple bond, has been largely used for the developement of novel synthetic methods and the construction of unusual N-bearing heterocycles. The reaction versatility of ynamide on umpolung reactivity, radical reactions and asymmetric synthesis have been recently reviewed. This review provides an overall scenic view into the gold catalyzed transformation of ynamides. The ynamides reactivity towards nitrogen-transfer reagents, such as azides, nitrogen ylides, isoxazoles, and anthranils; oxygen atom-transfer reagents, like nitrones, sulfoxides, and pyridine N-oxides; and carbon nucleophiles under gold catalysis are herein uncovered. The scope as well the mechanistic insights of each reaction is also briefed.

Illustrated herein is a Pd(II) catalyzed one-pot direct difunc-tionalization of two distinct C(sp3)-H bonds [gem-ʹ-di-Me groups bearing aliphatic carboxylic acid] with bifunctional reagent (BFR) 2-iodo benzoic acid. The methyl 2-pyridyl sul-foximine (MPyS) bidentate directing group (DG), 2-chloro-5-trifluoromethyl ligand, and NaBrO3 co-oxidant combination helps the concerted metalation deprotonation (CMD) of inert C(sp3)-H bond as well reductive elimination steps; density functional theory (DFT) studies validate such insights. This process makes two [CC and CO] bonds of gem-ʹ-di-Me groups of DG-enabled aliphatic carboxylic acids in a single operation offering access to unusual benzo-fused peripheral substituted ω-membered lactones. This concept is uncovered for the first time. The transformation tolerates labile functional groups featuring broad scope with the construction of wide range of novel molecules of structural diversity. Ki-netic and control experiments study reveal the participation of monomeric-Pd-species on the catalytic cycle. Synthetic versatility of the complex molecular entities is also presented.

Developed herein is a Cu(II)-catalyzed Meyer-Schuster-type rearrangement of alkyne-tethered cyclohexadienone for the construction of m-enone-substituted phenols. The reaction involves an uncommon 5-exo-trig 1,6-enyne cyclization of alkyne-tethered-cyclohexadienone, aromatization-triggered C-O bond cleavage, and an electrocyclic 4π-ring-opening of oxetene intermediate. This atom-efficient transformation provides access to a wide range of synthetically important α-(m-substituted phenol)-α,β-unsaturated ketones, featuring a broad scope with labile functional group tolerance. The gram-scale demonstration makes this transformation synthetically viable. The synthetic application of α,β-unsaturated ketones is also showcased.

An unconventional cobalt(iii)-catalyzed one-pot domino double annulation of aryl thioamides with unactivated alkynes is presented. Sulfur (S), nitrogen (N), and o,o′-C–H bonds of aryl thioamides are involved in this reaction, enabling access to rare 6,6-fused thiopyrano-isoquinoline derivatives. A reverse ‘S’ coordination over a more conventional ‘N’ coordination of thioamides to the Co-catalyst specifically regulates the formation of four [C–C and C–S at first and then C–N and C–C] bonds in a single operation, a concept which is uncovered for the first time. The power of the N-masked methyl phenyl sulfoximine (MPS) directing group in this annulation sequence is established. The transformation is successfully developed, building a novel chemical space of structural diversity (56 examples). In addition, the late-stage annulation of biologically relevant motifs and drug candidates is disclosed (17 examples). The preliminary photophysical properties of thiopyrano-isoquinoline derivatives are discussed. Density functional theory (DFT) studies authenticate the participation of a unique 6π-electrocyclization of a 7-membered S-chelated cobaltacycle in the annulation process., A Co-catalyzed one-pot double annulation of sulfoximine bearing thioamides with alkynes for the synthesis of [6,6]-fused thiopyrano-isoquinolines is disclosed. The annulation involves a 6π-electrocyclization of 7-membered S-chelated cobaltacycle.

A wide array of methoxy-substituted-polynitro-aryl-pyrazole/imidazoles with readily oxidizable -NH

Direct difunctionalization of chemically distinct ortho- and peri-C–H bonds of fused hetero(arenes) is illustrated through an unusual one-pot domino {[4 + 2] & [5 + 2]} double annulation with alkynes for the first time. This process is viable under Ru(II)-catalysis using a sulfoximine directing group and builds four bonds [(C–C)–(C–N) and (C–C)–(C–O)] in a single operation. Such synthetic manifestation offers access to uncommon [6,7]-fused oxepino-pyridine skeletons. DFT calculations provide mechanistic insight into this double annulation of naphthoic acid derivatives with alkynes and corroborate the participation of a ruthena-oxabicyclooctene intermediate, which is responsible for the rare 7-membered ring formation.

The sulfur and nitrogen moieties of methylphenyl sulfoximine (MPS)-enabled aryl thioamides are independently involved in annulation with unactivated alkynes to construct the unusual 6,6-fused thiopyranoisoquinoline skeletons. The MPS directing group plays a vital role in making this unprecedented Ru-catalyzed one-pot double annulation of aryl thioamides with alkynes chemo- and regioselective. Both the o,o'-C-H bonds of the aryl motif are sequentially functionalized to form four bonds [C-C, C-S and C-C, C-N] in a single operation by overcoming the undisputed challenges, viz. the "S" poisoning effect on the transition-metal catalyst and the susceptibility of S to oxidation. The novel isothiochromene-1-one skeletons are successfully constructed, as the annulation is initiated with S in preference over the N motif of thioamides with alkynes. The preliminary photophysical properties of the thiopyrano-isoquinoline derivatives are also discussed.

π-Extended tetrasubstituted olefins are widely found motifs in natural products, leading drugs, and agrochemicals. Thus, development of modular strategies for the synthesis of complex all-carbon-substituted olefins always draws attention. The difunctionalization of unsymmetrical alkynes is an attractive approach but it has remained faced with regioselectivity issues. Here we report the discovery of a regio- and stereoselective syn-1,2-dicarbofunctionalization of unsymmetrical internal alkynes. A cationic Pd-catalyzed three-component coupling of aryl diazonium salts, aryl boronic acids (or olefins) and yne-acetates enables access to all-carbon substituted unsymmetrical olefins. The transformation features broad scope with labile functional group tolerance, building broad chemical space of structural diversity (94 molecules). The value of this synthetic method is demonstrated by the direct transformation of natural products and drug candidates containing yne-acetates, to enable highly substituted structurally complex allyl acetate analogues of biologically important compounds. Synthetic versatility of the carboxylate bearing highly substituted olefins is also presented. The reaction outcome is attributed to the in situ formation of stabilized cationic aryl-Pd species, which regulates regioselective aryl-palladation of unsymmetrical yne-acetates. Control experiments reveal the synergy between the carboxylate protecting group and the cationic Pd-intermediate in the regioselectivity and reaction productivity; density functional theory (DFT) studies rationalize the selectivity of the reaction.

Reported is the discovery of an approach to regio- and stereoselective syn-1,2-dicarbofuctionalization of unsymmetrical alkynes. A cationic Pd-catalyzed three-component coupling of two distinct carbon-bearing functionalities aryl diazonium salts and aryl boronic acids/olefins with unsymmetrical alkynes enables accessing to all-carbon substituted unsymmetrical olefins. The transformation features broad scope with labile functional group tolerance building a novel chemical space of structural diversity (82 molecules) and is scalable. The cationic Pd species plays crucial; notably, density functional theory (DFT) studies establish this observation. Synthetic versatility of the modifiable carboxylate bearing highly-substituted olefins is also presented.

Reported herein is a syn-thioallylation of ynamides incorporating a sulfide moiety at the α-position and an allyl group at the β-position of the ynamide. The transformation is successful under ytterbium(III)-catalysis, providing access to highly substituted thioamino-skipped-dienes with broad substrate scope. Thus, tetrasubstituted olefins (with four different functional groups: amide, phenyl, thioaryl/alkyl, and allyl on the carbon centers) are made in a single step from readily accessible ynamides, preserving complete atom economy. The reaction can be extended to the synthesis of selenoamino dienes by ynamide syn-selenoallylation. DFT studies and control experiments provide insight into the reaction mechanism.

A direct Pd(ii)-catalyzed kinetic resolution of heteroaryl-enabled sulfoximines through an ortho-C–H alkenylation/arylation of arenes has been developed. The coordination of the sulfoximine pyridyl-motif and the chiral amino acid MPAA ligand to the Pd(ii)-catalyst controls the enantio-discriminating C(aryl)–H activation. This method provides access to a wide range of enantiomerically enriched unreacted aryl-pyridyl-sulfoximine precursors and C(aryl)–H alkenylation/arylation products in good yields with high enantioselectivity (up to >99% ee), and selectivity factor up to >200. The coordination preference of the directing group, ligand effect, geometry constraints, and the transient six-membered concerted-metalation–deprotonation species dictate the stereoselectivity; DFT studies validate this hypothesis., A Pd/MPAA catalysed KR of heteroaryl substituted sulfoximines through C–H alkenylation and arylation (up to >99% ee) is developed. In-depth DFT studies uncover the salient features.

This study discloses the first enantioselective variant of the gold(I)-catalyzed hydrative cyclizations of ynamides, which have been implemented by using bis-gold(I) complexes of chiral diphosphines. Starting from N-propargyl-ynamides and water in the presence of p-toluenesulfonic acid, the cyclization reactions afford N-tosyl-3,6-dihydropyridin-2(1H)-ones in good isolated yields and with high levels of stereocontrol (20 examples, enantiomeric ratios up to 94:6).

A ruthenium (Ru)-catalyzed double annulation of easily accessible N-methoxybenzamide derivatives with unactivated alkynes for the synthesis of unusual 6,6-fused pyranoisoquinolines is described. Both ortho-C–H bonds of arenes and the N- and O-moieties of N-methoxybenzamides are involved in the construction of four [(C–C)–(C–N) and (C–C)–(C–O)] bonds in one step under single catalytic conditions. The unsymmetrical annulation of N-methoxybenzamides with two distinct alkynes is also demonstrated. The oxidizable directing group N-methoxyamine (NHOMe) assists the unsymmetrical double annulations of arenes [that use both N- and O-heteroatoms] in a single operation. This synthetic method features excellent substrate scope and tolerates a wide range of functional groups. Peripheral modification of pyranoisoquinolines for the construction of complex heterocyclic compounds is also demonstrated.

A. Cotarnine (1). A 250-mL, round-bottomed, three-necked flask is equipped with a magnetic stir bar (elliptical, 32 x 16 mm, Teflon-coated). The flask is dried under vacuum (1.8 mmHg) with a propane torch and then allowed to cool to 25 °C. The dried flask is then charged with nitric acid (150 mL, 18% (v/v) in H2O) and fitted with a reflux condenser complete with a nitrogen inlet, a thermometer, and the final neck is sealed with a rubber septum (Figure 1) (Notes 2, and 3). Slow stirring of the solution (150 rpm) is commenced. The rubber septum is briefly removed, the solid (S,R)-Noscapine (20 g, 48.4 mmol, 1.0 equiv) is added to the flask in a single portion at 25 °C, after which the rubber septum is replaced (Notes 4 and 5). The mixture is observed to turn from a white to slightly yellow turbid solution.

Ynamides are typically more reactive than simple alkynes and olefins. However, a serendipitous observation revealed a rare case where the reactivity of simple alkynes exceeds that of ynamides. This led to the development of a unique sulfur-radical-triggered cyclization of yne-tethered ynamides, which involves attack of the alkyne by a thiyl radical followed by cyclization with the ynamide. A wide range of novel 4-thioaryl pyrroles that could tolerate common functional moieties and N-protecting groups were expediently constructed by this strategy. The current method contrasts with the typical cyclization of yne-ynamides, which involves the attack of the alkyne moiety by the ynamide core. Control experiments and DFT calculations supported the participation of the sulfur radical in the reaction and the regioselective cyclization. The synthetic potential of the substituted pyrroles is also discussed.

A regioselective sulfonyl/sulfinyl migration cycloisomerization cascade of alkyne-tethered ynamides is developed in the presence of XPhosgold catalyst. This reaction is the first example of a general [1,3]-sulfonyl migration from the nitrogen center to the β-carbon atom of ynamides, followed by umpolung 5-endo-dig cyclization of the ynamide α-carbon atom to the gold-activated alkyne, and final deaurative [1,5]-sulfinylation. This process allows the synthesis of peripherally decorated unconventional 4-sulfinylated pyrroles with broad scope from N-propargyl-tethered ynamides. In contrast, N-homopropargyl-tethered ynamides undergo intramolecular tetradehydro Diels-Alder reaction to provide 2,3-dihydro-benzo[f]indole derivatives. Control experiments and density-functional theory studies were used to study the reaction pathways.

An unconventional cobalt(III)-catalyzed one-pot domino double annulation of aryl thioamides with unactivated alkynes is presented. Sulfur (S), nitrogen (N), and o,o'-C-H bonds of aryl thioamides are involved in this reaction, enabling access to rare 6,6-fused thiopyrano-isoquinoline derivatives. A reverse ‘S’ coordination over more conventional ‘N’ coordination of thioamides to Co-catalyst specifically regulates the formation of four [C-C and C-S at first and then C-N and C-C] bonds in a single operation, a concept which is uncovered for the first time. The power of the N-masked methyl phenyl sulfoximine (MPS) directing group in this annulation sequence is established. The transformation is successfully developed, building a novel chemical space of structural diversity (56 examples). In addition, late-stage annulation of biologically relevant motifs and drug candidates are disclosed (17 examples). Preliminary photophysical properties of thiopyrano-isoquinoline derivatives are discussed. Density functional theory (DFT) studies authenticate the participation of a unique 6p-electrocyclization of a 7-membered S-chelated cobaltacycle in the annulation process.

A three-component Pd-catalyzed coupling of ynamides, aryl diazonium salts, and aryl boronic acids for the synthesis of novel triaryl-substituted enamides is described. This transformation represents the first example of an umpolung regioselective unsymmetrical syn-1,2-diarylation/aryl-olefination of ynamides. The aryl moieties of the diazonium salt (electrophile) and boronic acid (nucleophile) are explicitly incorporated in the electrophilic α- and nucleophilic β-position, respectively, of the ynamide, resulting in a single isomer of the N-bearing tetrasubstituted olefin. The scope is broad (68 examples), showing excellent functional-group tolerance. DFT calculations substantiate the rationale of the mechanistic cycle and the regioselectivity. The chemoselectivity and synthetic potential of the enamide products were also studied.

An unprecedented ruthenium (Ru)-catalyzed twofold unsymmetrical annulation of 3-O/N-allyl benzoic acid derivatives with isocyanates for the construction of dihydro-furan/indole-fused phthalimide scaffolds is discussed. This double-unsymmetrical functionalization of both o,o’-C–H bonds of arene moiety is explicitly viable under the influence of methylphenyl sulfoximine directing group constructing three different [C–C/C–C­(O)/N–C­(O)] bonds under a single catalytic system. A broad scope with all six-carbon-substituted arene motifs, control experiments, and gram-scale synthesis make the synthetic model viable and significant.

An uncommon sulfur → selenium → carbon radical transfer process is employed to develop an unprecedented selenyl radical-mediated regioselective cyclization of yne-tethered-ynamides. Density functional theory studies and HRMS experiments are used to establish a reactivity scale between thiyl and selenyl radicals. The unique features of this transformation include, (1) the chemoselective reactivity of RSe˙ over RS˙, (2) regioselective RSe˙ attack on alkyne over ynamide, (3) 5-exo-dig cyclization of yne-ynamide to unusual 4-selenyl-pyrroles, and (4) the green synthetic method. The reaction of methyldiselenide with yne-ynamides to methylselenopyrroles is also described.

A Ru-catalyzed intramolecular hydroarylation of arenes in an aqueous medium is presented herein. With the aid of methyl phenyl sulfoximine or an amide directing group, this atom-efficient hydroarylation of arenes ensued dihydrobenzofuran derivatives. Sequential double hydroarylation of arene motifs resulted in highly peripheral-decorated heterocycles. Deuterium labeling studies and control experiments offer valuable information in understanding the reactivity and the mechanistic data.

A nontrivial Ru-catalyzed one-pot sequential oxidative coupling of a (hetero)arene/vinylic/chromene system with alkyne and quinone is presented; the methyl phenyl sulfoximine (MPS) directing group is vital. This cyclization forms four (two C–C and two C–N) bonds in a single operation and produces unusual spiro-fused-isoquinolones with a broad scope. The release of phenyl methyl sulfoxide makes the MPS group transformable. A deuterium scrambling study sheds light on the reaction path.

A novel AlCl3-catalyzed intermolecular oxidative annulation of N-arylthio phthalimide derivatives with alkynes is showcased at room temperature. The annulation involves oxidative cleavage of the SN bond and the occurrence of 1,2-S-migration, which eventually allows the construction of diverse arrays of -conjugated 6-substituted 2,3-diaryl benzo[b]thiophene derivatives.

Silver-catalyzed cyclization and cycloisomerization of ketene N,N-acetals at room temperature has been developed to access a variety of highly substituted cyclobutene-fused azepine and 1,2-dihydropyridine derivatives. This cost-effective method is reliably implemented for the gram-scale synthesis of azepine and dihydropyridine derivatives. The iodo group in the periphery of the dihydropyridine motif can be functionalized with both Suzuki and Sonogashira reactions.

A workable cost-efficient synthetic method for the construction of nitro substituted tetrazole-N-aryl/heteroaryl derivatives is discussed here. The energetic functional groups –NO2, –NHNO2 and –N3 are reliably inserted into the molecular backbone, making the tetrazole-N-aryl derivatives highly energetic and insensitive to heat and impact. For example, the tetrazole derivatives 7 and 8, bearing a –NO2 or a –NHNO2 group, exhibit energetic properties close to RDX, but with enhanced insensitivity. Most of the synthesized compounds show exothermic decomposition and are consequently useful for energetic material applications.

Demonstrated herein is an AuI -catalyzed annulation of sulfonyl-protected ynamides with substituted 1,2-benzisoxazoles for the synthesis of E-benzo[e][1,3]oxazine derivatives. The transformation involves the addition of benzisoxazole to the gold-activated ynamide, ring expansion of the benzisoxazole fragment to provide an α-imino vinylic gold intermediate, and 1,2-migration of the sulfonamide motif to the masked carbene center to deliver the respective ring-expanded benzo[e][1,3]oxazine of predominant E configuration. A trapping experiment justifies the participation of the α-imino masked gold carbene. DFT computations also support the hypothesized mechanism and rationalize the product stereoselectivity.

A ruthenium (Ru)-catalyzed double annulation of easily accessible

We herein demonstrated a N-hydroxyphthalimide (NHPI)-mediated chemo- and regioselective radical cyclization of yne-dienone with thiols to construct 3-thioaryl bearing [6,6]-fused dihydrochromenone derivatives. This transformation tolerates common functional groups and has broad scope. The reaction proceeds via the attack of a thioaryl radical to alkyne over the activated Michael acceptor. The TEMPO quenching experiment suggests the involvement of a radical intermediate. Synthetic versatility of 3-thioaryldihydrochromenones is also showcased.

Presented herein is a gold(I) catalyzed intramolecular tetradehydro-Diels-Alder (TDDA) reaction of alkyne-tethered-ynamides for the construction of structurally complex 2,3-dihydrobenzo[f]indole derivatives. The mechanism of the regioselective benzannulation reaction was rationalized by means of density functional theory (DFT) calculations. Substrates having an aryl group at the ynamide terminus are exclusively participating in this TDDA reaction under gold catalysis.

Characterization and classification of rice growing soils of rainfed region of West Bengal is having an utmost importance for developing optimal agricultural land use planning. In the context of ever increasing food demand under dwindling agricultural land availability, rainfed areas have got the attention for enhancing food grain production for the national food basket. Hence, in the present study, we made an effort to characterize six rice growing soils placed in six different landform situations (plateau top, dissected plateau, plateau fringe, undulating upland, alluvial plains and valley fill) and classify accordingly for resource inventory of Rajnagar block, Birbhum district, West Bengal. Results depicted that, rice is grown mainly in Alfisols and Inceptisols in this block with varying morphological and physico-chemical characteristics. The soils are moderately deep to very deep with sandy loam to clay loam surface texture. Soils of plateau top, dissected plateau, plateau fringe, undulating upland, alluvial plains and valley fill were classified as Typic Haplustalfs, Aeric Endoaqualfs, Typic Haplustalfs, Typic Haplustepts, Aeric Endoaquepts, Typic Haplustalfs, respectively. The double crop rice ecology (rice-mustard) showed significantly (P=0.05) higher surface soil organic carbon (SOC) stock in surface as compared to the other monocrop rice ecologies. Among all the landforms compared, soils of valley fill region had the highest surface SOC stock (14.5 Mg ha-1) followed by plains (10.4 Mg ha-1), plateau fringe (7.7 Mg ha-1), plateau top (8.1 Mg ha-1), dissected plateau (7.2 Mg ha-1) and upland (6.9 Mg ha-1). Significantly (P=0.05) higher total profile SOC stock suggested a better soil health in valley fill and plains as compared to other areas that enhances our understanding about the need of the implementation of carbon management based land use planning for higher future productivity of these soils under environmental sustenance.

Developed is an unprecedented Au(I)-catalyzed syn-1,2-difunctionalization of ynamides with 2-aminobenzonitriles via nitrile activation. The coupling between ynamides and 2-aminobenzonitriles is explicitly regioselective, providing a straightforward access to 2,4-diamino-substituted quinolines. Density functional theory (DFT) study provides insightful information and rationalizes the reaction pathway. It shows how the synergy between ynamide π-activation and nitrile σ-coordination by the Au(I) catalyst makes the cyclization viable.

The paper reports the time-domain THz spectroscopy studies of noncentrosymmetric energetic nitro/nitrogen-rich aryl-tetrazole high-energy molecules. The fingerprint spectra in the THz domain reveal the role of different functional groups attached to position “1” of the tetrazole moiety, which controls the energetic properties. These responses are deliberated through density functional theory (DFT) calculations. The synthesized aryl-tetrazoles exhibit high positive heat of formation (369–744 kJ/mol), high detonation velocities, and pressures (Dv: 7734–8298 m·s–1; Dp: 24–28 GPa) in comparison to the noncentrosymmetric 2,4,6-trinitrotoluene (TNT). These compounds exhibit variation in the refractive indices and absorption between 0.1 and 2.2 THz range. The DFT studies at the molecular and single-crystal level (using plane wave pseudo potential method) endorse in detecting these bands (with ∼1% deviation). The calculated vibrational frequencies and linear optical properties are found to have good agreement with the experimental data in UV–visible and THz regions.

Polynitro aryl-azole (pyrazole and imidazole) derivatives were successfully synthesized and characterized by IR, NMR [1H, 13C], HRMS and differential scanning calorimetry (DSC-TGA). Some of the compounds (5,10&11) were also characterized by single crystal X-ray diffraction (XRD). The physicochemical properties for the synthesized (5,8,10,11&13) compounds were investigated among the all compounds 8 exhibit excellent calculated detonation properties superior to RDX and HMX.