α-Oxoketene-S,S-, N,S- and N,N-acetals: Versatile intermediates in organic synthesis

[3+3] Benzannulations of benzenoid- and heteroaromatic-ring systems

Bidentate Lewis Acids for the Activation of 1,2‐Diazines – A New Mode of Catalysis

A highly efficient and regioselective annulation protocol for a series of linearly 2,3- and angularly 1,2-substituted and annulated pyrido[1,2-a]benzimidazoles involving [3 + 3] cyclocondensation of the dianions generated from 2-methyl (2A) and 2-cyanomethyl (3A) benzimidazoles with a variety of α-oxoketene dithioacetals has been reported. Thus the dianion 2A derived from 2-methylbenzimidazole has been shown to undergo regioselective 1,2-addition with various α-oxoketene dithioacetals derived from acyclic (4a-d) and cyclic ketones (13a,b, 20, 29 and 32) to afford various carbinol acetals which on intramolecular cyclocondensation in the presence of phosphoric acid furnish the corresponding 1-methylthio-2,3-substituted (5a-c) and 2,3-fused linear polycyclic (14a,b, 21, 30, and 33) pyrido[1,2-a]benzimidazoles in high yields. Similarly the dianion 3A from 2-cyanomethylbenzimidazole undergoes one-pot conjugate addition-elimination and cyclocondensation with these α-oxoketene dithioacetals to give 4-cyano-3-(methylthio)-1(or 1,2-)-substituted (6a-d) and the corresponding angularly 1,2-fused (16a,b, 23, 31, and 34) polycylic analogues of pyrido[1,2-a]benzimidazoles in execellent yields.

Heteroaromatic Annulation of 2-Methyl/2-Cyanomethylbenzimidazole Dianions with α-Oxoketene Dithioacetals: A Highly Regioselective Synthetic Protocol for 1,2- and 2,3-Substituted/Annulated Pyrido[1,2-a]benzimidazoles†

Novel aryl polycyclic aromatic hydrocarbons: Phenylphenanthrene and phenylanthracene identification, occurrence and distribution in sedimentary rocks

Cycloaromatization of ∝-oxoketene dithioacetals with 3-methyl-5-lithiomethylisoxazole: A new general approach for synthesis of substituted and annelated 1,2-benzisoxazoles☆

Cycloaromatization of δ-oxoketendithioacetals with benzylmagnesium chloride: A novel naphthalene annelation reaction

Cycloaromatization of α-oxoketene dithioacetals and β-oxodithioacetals with benzyl-,1-(naphthylmethyl) and 2-(naphthylmethyl)magnesium halides: Synthesis of condensed polynuclear aromatic hydrocarbons

Studies on cycloaddition reactions of 1,3-diphenyl-2-azaallyl lithium and ethyl (benzylideneamino) acetate anion with α-oxoketene dithioacetals

(3-Dimethylamino-2-propenoyl)ketene dithioacetals 3a-c, obtained by condensation of the corresponding acylketene dithioacetals 1a-c with dimethylformamide diethyl acetal, undergo 1,4-additions with alkyl Grignard reagents (RMgX, R = CH 3 , C 2 H 5 , n-C 3 H 7 and i-C 3 H 7 ) on the enaminone moiety to afford the title compounds 4a-l in good yields.

A facile route to 5-alkyl-1,1-bis(methylthio)penta-1,4-dien-3-ones

M. P. Balu

Papers

Cycloaromatization of ∝-oxoketene dithioacetals with 3-methyl-5-lithiomethylisoxazole: A new general approach for synthesis of substituted and annelated 1,2-benzisoxazoles☆

Cycloaromatization of δ-oxoketendithioacetals with benzylmagnesium chloride: A novel naphthalene annelation reaction

Cycloaromatization of α-oxoketene dithioacetals and β-oxodithioacetals with benzyl-,1-(naphthylmethyl) and 2-(naphthylmethyl)magnesium halides: Synthesis of condensed polynuclear aromatic hydrocarbons

Studies on cycloaddition reactions of 1,3-diphenyl-2-azaallyl lithium and ethyl (benzylideneamino) acetate anion with α-oxoketene dithioacetals

A facile route to 5-alkyl-1,1-bis(methylthio)penta-1,4-dien-3-ones