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Reactions of a masked N‐heterocyclic phosphinidene (mNHP, 1), a four‐membered heterocycle with a divalent P atom, with various isonitriles (tBu−NC, Dmp−NC) and carbonyls (CO, Fe(CO)5, and benzalacetone) have been studied. The isonitriles (tBu−NC and Dmp−NC) insert into a P−N bond of the four‐membered ring of 1, leading to the formation of a five‐membered heterocycle (2tBu, 2Dmp), indicating carbene‐like reactivity of the isonitriles. In exactly this way, CO, which is isolobal to isonitriles, reacts to form a five‐membered ring (3) with an exocyclic C=O double bond. If, on the other hand, Fe(CO)5 is used as a CO source, a CO molecule is inserted analogously, however, the remaining Fe(CO)4 fragment is bound via a phosphorus‐iron dative bond to the five‐membered heterocycle. When mNHP 1 reacts with the α,β‐unsaturated ketone benzalacetone, phosphinidene reactivity is observed for 1. This means that the four‐membered ring opens and the P atom reacts with the benzalacetone in a cyclization reaction to form a 1,2‐oxaphospha‐cyclopentene. Theoretical studies of the five‐membered heterocycles 2 and 3 carrying eight π electrons show that zwitterionic Lewis representations dominate in the resonance scheme and only a very low biradical character (<5 %) is found. [ABSTRACT FROM AUTHOR]

A series of thienoindolizine structural isomers have been synthesized in a one‐pot, two‐step procedure starting from easily accessible gem‐difluoroalkene functionalized bromothiophenes. The developed method gives easy access to a range of thienoindolizine products containing thieno[3,2‐g]‐, thieno[3,4‐g]‐ and thieno[2,3‐g]indolizine core structures. The described synthesis strategy consists of a base mediated, transition metal free nucleophilic substitution of fluorine atoms by nitrogen containing heterocycles followed by a Pd catalyzed intramolecular cyclization. A series of 22 final product examples has been obtained with yields ranging from 29 % to 95 %. UV/Vis absorption, fluorescence spectroscopy, fluorescence lifetime measurements and cyclic voltammetry were carried out with selected final products to evaluate structural effects on photophysical and electrochemical properties. (TD)DFT and NICS calculations were performed to provide insight into the electronic properties of the four core molecular structures. [ABSTRACT FROM AUTHOR]

A new synthetic route to 1H-1,2,3-triazole-4,5-dithiols (tazdtH2) as ligands for the coordination of NiII, PdII, PtII and CoIII via the dithiolate unit is presented. Different N-protective groups were introduced with the corresponding azide via a click-like copper-catalyzed azide-alkyne [3 + 2] cycloaddition (CuAAC) and fully characterized by NMR spectroscopy. Possible isomers were isolated and an alternative synthetic route was investigated and discussed. After removal of the benzyl protective groups on sulfur by in situ-generated sodium naphthalide, complexes at the [(dppe)M] (M = Ni, Pd, Pt), [(PPh3)2Pt] and [(η5-C5H5)Co] moieties were prepared and structurally characterized by XRD analysis. In this process, the by-products 11 and 12 as monothiolate derivatives were isolated and structurally characterized as well. With regioselective coordination via the dithiolate unit, the electronic influence of different metals or protective groups at N was investigated and compared spectroscopically by means of UV/Vis spectroscopy and cyclic voltammetry. Complex [(η5-C5H5)Co(5c)] (10), is subject to a dimerization equilibrium, which was investigated by temperature-dependent NMR and UV/Vis spectroscopy (solution and solid-state). The thermodynamic parameters of the monomer/dimer equilibrium were derived. [ABSTRACT FROM AUTHOR]

The preparative access to and first group 10 metal complexes of novel 1H-1,2,3-triazole-4,5-dithiolate ligands (tazdt2−) are reported. A set of S-protected 1H-1,2,3-triazole-4,5-dithiol derivatives with R1 = 2,6-dimethylphenyl (Xy) or benzyl (Bn) at N1 and with R2 = Bn or trimethylsilylethyl (TMS-ethyl) at both S atoms were synthesized by a 1,3-dipolar cycloaddition catalysed by either Ru(II) or Cu(I). Extensive investigations on the removal of the protective groups resulted the reductive removal of benzyl groups to be superior in isolating the free 4,5-dithiols of R1N3C2(SH)2 with R1 = Xy (H2-8) or Bn (H2-9). Coordination of these ligands led to the formation of the metal complexes [(η5-C5H5)2Ti(8)], [Ni(dppe)(8)], [Ni(dppe)(9)], [Pd(dppe)(9)] {dppe = bis(diphenylphosphanyl)ethane} and homoleptic (NBu4)n[Ni(8)2] (n = 1, 2). All complexes were fully characterized including structure determination by single crystal XRD. The electronic properties of the Ni and Pd complexes were determined by cyclic voltammetry, UV/vis and EPR spectroscopy supported by DFT calculations. According to the spectral and electrochemical data, the tazdt2− complexes resemble the corresponding benzene-1,2-dithiolate (bdt2−) type compounds reflecting the restricted influence of the electron-withdrawing N3 moiety in the backbone. DSC-TGA measurements with [(η5-C5H5)2Ti(8)] and [Ni(dppe)(8)] indicate a well-defined thermal process involving simultaneous elimination of both N2 and CS. [ABSTRACT FROM AUTHOR]

The reaction of the singlet biradical [P(μ-NTer)]2 with various aldehydes selectively yielded the corresponding [2.1.1]-bicyclic addition products in a very fast reaction. All products were fully characterized, including by NMR and vibrational spectroscopy as well as single-crystal X-ray diffraction. The mechanism of the addition was investigated theoretically using high-level ab initio methods (CCSD(T) with triple- and quadruple-zeta basis sets) and corresponds to a concerted cycloaddition reaction with a very low activation barrier. For comparison, the mechanisms of the literature-known cycloadditions of H2, alkenes, and alkynes were also studied, indicating a similar reaction profile for all unsaturated reactants. [ABSTRACT FROM AUTHOR]

The reaction of the singlet biradical [P(μ-NTer)]2 with various aldehydes selectively yielded the corresponding [2.1.1]-bicyclic addition products in a very fast reaction. All products were fully characterized, including by NMR and vibrational spectroscopy as well as single-crystal X-ray diffraction. The mechanism of the addition was investigated theoretically using high-level ab initio methods (CCSD(T) with triple- and quadruple-zeta basis sets) and corresponds to a concerted cycloaddition reaction with a very low activation barrier. For comparison, the mechanisms of the literature-known cycloadditions of H2, alkenes, and alkynes were also studied, indicating a similar reaction profile for all unsaturated reactants. [ABSTRACT FROM AUTHOR]

A concise and modular synthesis of pyrrolo[1,2- a ][1,6]- and [1,8]naphthyridines by a one-pot two-step reaction consisting of electrophilic acylation followed by an alkyne-carbonyl-metathesis reaction as the final cyclization step is reported. This developed synthetic methodology allows the facile synthesis of these heterocyclic core structures in mainly high overall yields under metal-free conditions. Reaction conditions are carefully optimized and display a novel supplement to access these tricyclic heterocyclic compounds. [ABSTRACT FROM AUTHOR]

Mes*N(SiMe3)BiCl2 (1, Mes* = 2,4,6‐tri‐tert‐butylphenyl) can be referred to as a hidden iminobismuthane, Mes*N=BiCl, which was thought to be generated in‐situ upon Me3SiCl elimination triggered by a Lewis acid such as GaCl3. Therefore, the reactivity of aminobismuthane 1 was studied to find a synthesis route for the formation of a tetrazabismuthole in a [3+2] cycloaddition reaction with a covalently bound azide. However, reaction of 1 with GaCl3 cleanly led to [Mes*N(SiMe3)BiCl][GaCl4] (2[GaCl4]), a compound with a Bi‐arene σ‐complex. Utilizing Ag[WCA] salts (WCA = weakly coordinating anion) for chloride abstraction, a C–C coupling product (3) was identified. The diiodide species Mes*N(SiMe3)BiI2 (4) as precursor for a diazido species and the azido‐chloride compound Mes*N(SiMe3)Bi(N3)Cl (5) were also prepared to explore the possibility of a BiN4 heterocycle formation, again upon Me3SiX elimination (X = halogen, N3), but 4 and 5 were unstable towards decomposition into a black precipitate and a complex product mixture. The structure and bonding of all isolated bismuth species is discussed. Derivatives of the aminobismuthane Mes*N(SiMe3)BiCl2 were synthesized. Chloride abstraction with GaCl3 led to the formation of a bismuth‐arene σ‐complex. The process is reversible in the presence of a Lewis base like Me3SiN3 when the counter ion is [GaCl4]–. Abstracting a chloride anion by a silver salt containing a weakly coordinating anion led to C–C coupling products. [ABSTRACT FROM AUTHOR]

A dichloro-cycloazatriphosphane that incorporates a cyclic NP3 backbone could be synthesized using knowledge gained from the chemistry of N2P2 and P4 ring systems. It fills the gap between the congeneric compounds [ClP(μ-NR)]2 and [ClP(μ-PR)]2 (R=sterically demanding substituent), and thus contributes to the systematic development of nitrogen-phosphorus chemistry in general. The title compound was studied with respect to its formation via a labile aminodiphosphene, which readily underwent different rearrangement reactions depending on the solvent. All compounds were fully characterized by experimental and computational methods. [ABSTRACT FROM AUTHOR]

A range of aza-ullazines, which represent a new heterocyclic core structure, were synthesized through a scalable four-step reaction, including a Sonogashira reaction and metal-free cyclization promoted by p-toluenesulfonic acid. The optical and electrochemical properties of selected derivatives were investigated, they were found to have similar absorption and emission spectra but a higher oxidation potential than the parent ullazine core. [ABSTRACT FROM AUTHOR]

The reaction of [ClP(μ-PMes*)]2 ( 1) with the Lewis acid GaCl3 yielded a hitherto unknown tetraphosphabicyclo[1.1.0]butan-2-ium salt, [Mes*P4(Cl)Mes*][GaCl4] ( 3[GaCl4]), which incorporates a positively charged phosphonium center within its bicyclic P4 scaffold. The formation of the title compound was studied by means of low-temperature NMR experiments. This led to the identification of an intermediate cyclotetraphosphenium cation, which was trapped by reaction with dimethylbutadiene (dmb). All of the compounds were fully characterized by experimental and computational methods. [ABSTRACT FROM AUTHOR]

5,7-Dihydropyrido[3,2- b:5,6- b′]diindoles were prepared by a highly efficient two-step synthesis that involved a site-selective Suzuki coupling reaction of 2,3,5,6-tetrabromopyridine and a subsequent Pd-catalyzed cyclization that proceeded through a twofold C-N coupling reaction with aromatic and aliphatic amines. With the exception of the parent molecule, which was described in a patent without any characterization data, the 5,7-dihydropyrido[3,2- b:5,6- b′]diindoles are a new chemical entity. Their electrochemical and photochemical properties were investigated. These pyridodiindoles show promising fluorescence properties with good quantum yields and interesting electrochemical behavior. The optical and electronical properties were analyzed and explained by using DFT calculations. [ABSTRACT FROM AUTHOR]

A ring-ring transformation in the series of spiro[indole- 3,5'-pyrimido[4,5-b]quinoline]-2,2',4'-trione derivatives prepared by a three-component reaction of (thio)barbituric acids, electronrich aromatic amines, and isatins was observed. [ABSTRACT FROM AUTHOR]

Abstract: Highly functionalized ferrocenyl-substituted phenols were prepared by cyclization of masked or free dianions with 1,3-dielectrophilic 1-η5-ferrocenyl-3,3-bis(methylthio)prop-2-en-1-ones. While the cyclizations of 1,3-bis(silyloxy)-1,3-butadienes (masked dianions) proceed by initial 1,2-addition, the reactions of free 1,3-dicarbonyl dianions proceed by initial 1,4-addition. Therefore, both regioisomeric ferrocenylphenols are available from one and the same electrophile dependent on the type of nucleophile and reaction conditions employed. The reactions reported represent the first examples of the application of formal [3 + 3] cyclizations to the synthesis of organometallic compounds. [Copyright &y& Elsevier]

The [4+2] cycloaddition of 1-ethoxy-2-fluoro-1,3-bis(trimethylsilyloxy)-1,3-diene with dimethyl acetylenedicarboxylate (DMAD) afforded dimethyl 4-fluoro-3,5-dihydroxyphthalate. Site-selective Suzuki-Miyaura reactions of its bis(triflate) provide a convenient approach to 3,5-diaryl-4-fluorophthalates. [ABSTRACT FROM AUTHOR]

Functionalized anthraquinones were prepared by domino ‘twofold Heck-6π-electrocyclization’ reactions of 2,3-dibromo�naphthoquinone. [ABSTRACT FROM AUTHOR]

Hypersilyl(trimethylsilyl)aminodichlorophosphine, (hyp)N(SiMe3)PCl2, was treated with GaCl3, which resulted in the formation of an interesting novel bicycle, composed of a four-membered SiNP2 ring and a five-membered P2Ga2Cl ring. In the presence of Me3SiN3, the same reaction provided access to a cyclo-2-phospha-4-sila-1,3-diazenium tetrachlorogallate. The free chloro-cyclo-phosphasiladiazane was obtained by the addition of nucleophilic bases. [ABSTRACT FROM AUTHOR]

The [3+3] cyclocondensation of 1,3-bis(silyl enol ethers) with 1,1-bis(methylthio)-1-en-3-ones results in the regioselective formation of 3-(methylthio)phenols. The products represent useful synthetic building blocks, which are not readily available by other methods. [ABSTRACT FROM AUTHOR]

The formal [3+3] cyclocondensation of 1,3-bis(trimethylsilyloxy)buta-1,3-dienes with 1,1-bis(methoxy)trifluoromethyl-1-en-3-ones afforded functionalized 3-methoxy-5-(trifluoromethyl)phenols with very good regioselectivity. [ABSTRACT FROM AUTHOR]

The reaction of biradical [P(μ‐NTer)]2 (1, Ter = 2,6‐bis(2,4,6‐trimethylphenyl)phenyl) towards different alkenes (R = 2,3‐dimethyl–butadiene, 2,5‐dimethyl‐2,4‐hexadiene, 1,7‐octadiene, 1,4‐cyclohexadiene) and alkynes (R = 1,4‐diphenyl‐1,3‐butadiyne) was studied experimentally. Although these olefins can react in different ways, only [2+2] cycloaddition products (1R) were observed. The reaction with 2,3‐dimethylbutadiene also led to the [2+2] product (1dmb). Thermal treatment of 1dmb above 140 °C resulted in the recovery of biradical 1 upon homolytic bond cleavage of the two P–C bonds and the release of 2,3‐dimethylbutadiene. In contrast to this reaction, all other [2+2] additions products (1R, R = 1,7‐octadiene, 1,4‐cyclohexadiene, 1,4‐diphenyl‐1,3‐butadiyne) began to decompose at temperatures between 200 °C and 300 °C. Only unidentified products were obtained but no temperature‐controlled equilibrium reactions were observed. Computations were carried out to shed light into the formal [2+2] as well as the possible [4+2] addition reaction. [ABSTRACT FROM AUTHOR]

and heterocyclic benzoin derivatives were prepared by Sonogashira coupling of alkynes with 1,2-dihaloalkenes and subsequent oxidation of the alkyne to a 1,2-diketone. The Pd-catalyzed reaction of the product with (2-bromophenyl)boronic acid in the presence of phenylacetylene resulted in formation of cyclic benzoin derivatives by Suzuki-Miyaura reaction and subsequent Pd catalyzed nucleophilic addition to the carbonyl group. Hitherto unprecedented 5-hydroxy-5-phenylbenzo[ b ]naphtho[1,2- d ]thiophene-6(5H)-ones and their regioisomers were prepared from 2,3-dibromobenzothiophene. Phenanthrene benzoin derivatives were prepared from 2-bromo-1-iodobenzene. [Display omitted] [ABSTRACT FROM AUTHOR]

Tetraarylphthalates were prepared by SuzukiMiyaura reactions of dimethyl tetrabromophthalate. [ABSTRACT FROM AUTHOR]

In the title compound, C10H10N4O, the crystal packing is stabilized by intermolecular N—H⋯N hydrogen bonds between adjacent pyridine rings, resulting in a two-dimensional layer structure. The H atoms of the 4-methyl group are disordered [site occupation factors 0.643 (14) and 0.357 (14)]. [ABSTRACT FROM AUTHOR]

N,N′, N′-[Tris(trimethylsilyl)]hydrazino(dichloro)arsane, (Me3Si)2N-N(SiMe3)-AsCI2 (1), has been transformed into the corresponding N-trimethylsilyl-N′,N′-bis-(dimethylchlorosilyl)hydrazinodimethylarsane in a two-step synthesis: (i) Addition of GaCI3 to 1 results in the formation of the corresponding hydrazinodimethylarsane GaCI3 adduct (2). (ii) Reaction of 2 with 4-(dimethylamino)pyridine (DMAP) yielded the adduct-free hydrazinodimethylarsane (3). The intriguing methyl/chlorine exchange with GaCI3 as transfer/exchange reagent represents a new synthetic route to the hitherto unknown N-trimethylsilyl-N′,N′-bis-(dimethylchlorosilyl)hydrazinodimethylarsane in contrast to the same reaction of the phosphorus analogue that results in the formation of triazadiphospholes. The new exchange reaction was unambiguously proven by NMR and X-ray studies (1: monoclinic, P21/c, a = 9.5002(19) Å, b = 13.840(3) Å, c = 17.226(5) Å, ß = 120.12(2)°; V = 1959.1(8) Å3, Z = 4; 2: orthorhombic, Pbca; a = 11.7766(2) Å, b = 13.9927(2) Å, c = 28.3298(4) Å; V = 4668.37(12) Å3, Z = 4; 3: monoclinic, P21/c, Å = 12.015(2) Å, b = 12.466(3) Å, c 13.031(3) Å, ß = 98.20(3)°; V = 1931.8(7) Å3, Z = 4). Structural comparisons of the hydrazinoarsanes with their GaCI3 adducts provide interesting similarities and differences. Computations at the B3LYP level reveal that the exchange process is -34 kcal/mol exergonic. [ABSTRACT FROM AUTHOR]

Abstract: Starting from a [3+2] synthetic tool kit, new PN-heterocycles may be isolated according to a new synthetic approach called GaCl3-assisted [3+2] cycloaddition. According to this concept the dipolarophile Mes∗–NCl (Mes∗ =2,4,6-tri-tert-butylphenyl) was reacted with the 1,3-dipole (TMS)2N–N(TMS)–PCl2 (TMS=trimethylsilyl) yielding the kinetically stabilized [3+2] cycloaddition product triazadiphosphole, Mes∗N3P2, stabilized as GaCl3 adduct. Synthesis, structure and bonding are discussed. [Copyright &y& Elsevier]

Abstract: Fluoranthenes were prepared by domino two-fold Heck/electrocyclization/dehydrogenation reactions of 1,2-dibromoacenaphthylene. [Copyright &y& Elsevier]

Abstract: 6-Aryl-2,3-dihydro-4H-pyran-4-ones were prepared in one step by cyclocondensation of 1,3-diketone dianions with aldehydes. The use of hydrochloric acid (10%) for the aqueous work-up proved to be very important. [Copyright &y& Elsevier]

Abstract: Acetal-protected (2,4-dioxocyclohex-1-yl)acetic acid derivatives were prepared by the allylation of dilithiated 1,3-cyclohexane-1,3-diones, by the protection of the carbonyl groups and by the oxidation of the alkene. The products were then transformed, by amide formation and subsequent cyclization, into 2,6-dioxo-1,2,3,4,5,6-hexahydroindoles, which represent important intermediates for the synthesis of various alkaloids. [Copyright &y& Elsevier]

Ultrasound irradiation in presence of 20% ZnBr2 effectively promotes regio- and stereo-selective cycloaddition reaction of azomethine ylide with a series of (E)-3-benzylideneindolin-2-ones to afford 3,3'-dispiropyrrolidine bisoxindole derivatives in excellent yields in methanol at room temperature. The factors affecting the cycloaddition reaction, for example solvent, catalyst, ultrasonic irradiation, are examined in detail to find the mildest conditions and highest reaction yields. The structure and stereochemistry of cycloadducts were determined by spectroscopic data and confirmed by X-ray crystallographic analysis. [ABSTRACT FROM AUTHOR]

Title compounds are prepared under mild conditions by reaction of 3-halochromones with β-ketoamides and dihydroindolethiones. [ABSTRACT FROM AUTHOR]

Abstract: The UV‐VIS and fluorescence properties of some products are investigated. [ABSTRACT FROM AUTHOR]

The reaction of [ClP(μ-PMes*)]2 ( 1) with the Lewis acid GaCl3 yielded a hitherto unknown tetraphosphabicyclo[1.1.0]butan-2-ium salt, [Mes*P4(Cl)Mes*][GaCl4] ( 3[GaCl4]), which incorporates a positively charged phosphonium center within its bicyclic P4 scaffold. The formation of the title compound was studied by means of low-temperature NMR experiments. This led to the identification of an intermediate cyclotetraphosphenium cation, which was trapped by reaction with dimethylbutadiene (dmb). All of the compounds were fully characterized by experimental and computational methods. [ABSTRACT FROM AUTHOR]

The cyclization of 1,5-bis[(trimethylsilyl)oxy]penta-1,4-dienes with quinoxalines and chloroformates afforded 2,3,3a,9a-tetrahydro-1 H-cyclopenta[ b]quinoxaline-1,3,4,9-tetracarboxylate. [ABSTRACT FROM AUTHOR]

The cyclization of thiosemicarbazide with α-bromoacetophenone can result in the formation of isomeric 1,3,4-thiadiazines and two different thiazoles. We studied the use of 4-methyl- and 4-ethylthiosemicarbazide as dinucleophilic building blocks. In this context, we observed an unprecedented rearrangement of a 2-hydrazono-2,3-dihydrothiazole to a 1,3,4-thiadiazine. While ring contractions of 1,3,4-thiadiazines to thiazoles are quite common, ring enlargements are new. The course of the reaction depends on the substitution pattern of the substrate. [ABSTRACT FROM AUTHOR]

An efficient one-pot, three-component synthesis of novel dispiro[oxindole-3,3′-pyrrolidines] by 1,3-dipolar cycloaddition of azomethine ylides, in situ generated by reaction of 1,2-diones with sarcosine and subsequent decarboxylation, with a series of ( E)-3-benzylidene-2,3-dihydro-1 H-indol-2-ones is reported. Molecular complexity is generated in only one synthetic step. All reactions proceed with excellent regioselectivity and in good-to-excellent yields. The workup is easy, the reaction times are short, and no catalyst is required. [ABSTRACT FROM AUTHOR]

A variety of 6-(trichloromethyl)salicylates (=2-hydroxy-6-(trichloromethyl)benzoates) were prepared by TiCl4-mediated cyclization of 1,3-bis(trimethylsilyloxy)buta-1,3-dienes with 1,1,1-trichloro-4,4-dimethoxybut-3-en-2-one. The employment of trimethylsilyl trifluoromethanesulfonate (Me3SiOTf) as Lewis acid resulted in the formation of trichloromethyl-substituted cyclohexenones. The cyclizations proceeded with good-to-very-good regioselectivities. [ABSTRACT FROM AUTHOR]

Abstract: Indole-2(3H)thiones were cyclized under the action of 2-fluorobenzoyl chlorides to give thiochromeno[2,3-b]indol-11(6H)-ones or under the action of 2-chloronicotinoyl chlorides to give pyrido[3′,2′:5,6]thiopyrano[2,3-b]indol-5(10H)-ones. The reaction of cyclization proceeds regioselectively in DMF and does not require transition metals for completion. Obtained heterocycles are isosteric analogues of various tetracyclic indole derived alkaloids. [Copyright &y& Elsevier]

Abstract: The cyclization of 1,3-bis(trimethylsilyloxy)-1,3-butadienes with 3-oxo-bis(methylthio)ketenacetals afforded 3-(methylthio)phenols containing an acyl or ester substituent located at position 2. The cyclization of free 1,3-dicarbonyl dianions with 3-oxo-bis(methylthio)ketenacetals resulted in the formation of regioisomeric products containing an acyl group located at position 6. [Copyright &y& Elsevier]

Abstract: The cyclization of fluoroalkylated 3,5-dioxoesters with hydrazines, carried out in glacial acetic acid, afforded pyrazines with fluoroalkylated side-chain. The cyclization of 3,5-dioxoesters with hydroxylamine afforded hydroxylated fluoroalkylated dihydroisoxazoles. All reactions proceeded with good to very good regioselectivity. [Copyright &y& Elsevier]

Abstract: An efficient palladium-catalyzed cyclization of o-chlorohetaryl ynones with aliphatic and aromatic primary amines represents a simple access to a wide range of benzo[b][1,8]naphthyridin-4(1H)-one and pyrido[2,3-b]quinoxalin-4(1H)-one derivatives in good to excellent yields. [Copyright &y& Elsevier]

Abstract: The synthesis of 1-deazapurines and isosteres bearing the exocyclic nitrogen atom at position-1 was developed basing on the formal [3+3]-cyclization reaction of nitro-malonaldehyde with the set of electron-excessive aminoheterocycles. Through the functionalization of the purine-like scaffolds synthesized the diversity of compounds furnished in the possition-1 with aryl, alkinyl, and vinyl rests, were obtained. [Copyright &y& Elsevier]

Abstract: Benzothiophenes and dibenzothiophenes were prepared by twofold Heck reactions of 2,3-dibromothiophene and 2,3-dibromobenzothiophene, respectively, and subsequent thermal 6π-electrocyclization. The Heck reaction of 2,3-dibromothiophene and 2,3-dibromobenzothiophene with 1 equiv of alkenes proceeded with different regioselectivities and afforded 2-alkenylthiophenes and 3-alkenylbenzothiophenes. [Copyright &y& Elsevier]

Functionalized 5-alkyl-3-(trifluoromethyl)phenols were prepared by formal [3+3] cyclization of 1,3-bis(silyloxy)buta-1,3-dienes with 1,1,1-trifluoro-4-(silyloxy)alk-3-en-2-ones derived from 1,1,1-trifluoroalkane-2,4-diones. The latter were prepared by condensation of the dianion of 1,1,1-trifluoropentane-2,4-dione with alkyl halides. [ABSTRACT FROM AUTHOR]

Abstract: A concise and efficient approach to a series of chromen-4-ones with fused thiophene ring has been developed using the Suzuki–Miyaura reaction of bromothiophene-2- and 3-carboxylates with 2-methoxyboronic acids and subsequent cyclization of prepared alkyl (2-methoxy)aryl thiophene-2- and 3-carboxylates under the action of BBr3/KOtBu. Starting bromothiophenes are easily obtained from corresponding commercially available aminothiophenes by diazotization/bromination reaction. [Copyright &y& Elsevier]

Abstract: The reaction of thiooxindoles with various 2- and 3-substituted pyridinium salts afforded a variety of functionalized thiazocinoindoles. The products have been prepared in good to excellent yields by regioselective dinucleophilic C/S-cyclocondensation of thiooxindoles with pyridinium salts. [Copyright &y& Elsevier]

(Me3Si)2CNN isomerizes upon addition of traces of [Me3Si]+ ions to give (Me3Si)2NNC, which then undergoes an unusual trimerization reaction to give exclusively 4-diazenyl-3-hydrazinylpyrazole. As catalyst the isonitrilium ion, [(Me3Si)2NNC(SiMe3)]+, was identified and fully characterized. Experiments and computations indicate a three-step reaction including isomerization of diazomethane, a C-C or N-C coupling, and a formal cycloaddition reaction. The kinetics and thermodynamics are discussed on the basis of DFT calculations. [ABSTRACT FROM AUTHOR]

Abstract: The TiCl4-mediated [3+3] cyclocondensation of 1,3-bis(silyloxy)-1,3-butadienes with 1-chloro-1,1-difluoro-4,4-dimethoxybut-3-en-2-one or 1,1-difluoro-4,4-dimethoxybut-3-en-2-one afforded CF2Cl- and CF2H-substituted salicylates, respectively. The Me3SiOTf-mediated [3+3] cyclocondensation of the same building blocks provided CF2Cl- and CF2H-substituted pyran-4-ones and CF2Cl-substituted cyclohexenones. The formation of CF2H-substituted cyclohexenones was not observed. Besides the type of Lewis acid, the product distribution is also influenced by the substitution pattern of the 1,3-bis(silyloxy)-1,3-butadiene: The Me3SiOTf mediated cyclization of C4-unsubstituted dienes resulted in the formation of CF2Cl-substituted pyran-4-ones, while the cyclization of C4-substituted dienes afforded CF2Cl-substituted cyclohexenones. The TiCl4-mediated cyclization of C4-substituted dienes with 1,1-difluoro-4,4-dimethoxybut-3-en-2-one failed. Therefore, 3-substituted CF2H-salicylates were prepared by transformation of the respective CF2Cl-salicylates with tributyltin hydride. [Copyright &y& Elsevier]

Abstract: Trifluoromethyl-substituted fluorenes, dibenzofurans, 9,10-dihydrophenanthrenes and 6H-benzo[c]chromenes were prepared by formal [3+3] cyclizations of 1,3-bis(trimethylsilyloxy)-1,3-butadienes. The reactions proceeded with very good regioselectivity. The product distribution depends on the type of 1,3-dielectrophile employed and can be explained by electronic reasons. [Copyright &y& Elsevier]

(Benzyloxycarbonyl)-protected 3,4-benzo-7-hydroxy-2,9-diazabicyclo[3.3.1]non-7-enes were prepared by one-pot cyclizations of 1,3-bis(silyl enol ethers) with quinazolines. Subsequent hydrogenation resulted in one-pot deprotection and rearrangement to give 2-(2-aminophenyl)-2,3-dihydropyridin-4(1 H)-ones. [ABSTRACT FROM AUTHOR]

Abstract: Difluoromethyl-containing heteroannulated pyridines, pyrimidines and pyrazoles are prepared by a two step method. The regioselective cyclizations of electron-excessive aminoheterocycles, hydrazines and amidines with CF2Cl-substituted 1,3-dicarbonyl compounds provide the corresponding CF2Cl-substituted heterocycles. Subsequent radical reactions with trimethylstannane or allyltrimethylstannane gave difluoromethyl-containing heteroannulated pyridines, pyrimidines and pyrazoles, respectively. [Copyright &y& Elsevier]