A facile synthesis of 3-cyclopropyl- and 5-cyclopropyl-isoxazoles

The regioselective synthesis of isomeric isoxazoles 3-(2-arylcyclopropyl)-5-methylthio- and 5-(2-arylcyclopropyl)- 3-methylthio-isoxazoles is described

Reaction of β-oxodithioesters with propargylamine: a facile entry to novel 2-(acylalkylidene)-5-(methylene)thiazolidines

Reaction of β-oxodithioesters derived from acyclic and cyclic ketones with propargylamine affords novel 2-(acylalkylidene)-5-(methylene)-thiazolidines in high yields by intramolecular nucleophilic attack of thiocarbonyl sulfur on the triple bond of the β-oxo-N-propargylthioamide intermediates

Trimethylsilyl chloride assisted conjugate addition-elimination of organocopper reagents to 2-bis(methylthio)nitroethylene: an efficient and highly stereoselective synthesis of 2-methylthio-2-alkyl/aryl-1-nitroethylenes and their application for synthesis of nitroheterocycles

An efficient method for the synthesis of novel 2-methylthio-2-alkyl/aryl-1-nitroethylenes 2 has been developed via conjugate addition-elimination of organocopper reagents to nitroketene dithioacetal 1 in the presence of TMSCl. The product nitroethylenes 2 have been further utilized for the synthesis of substituted 3-nitro-2-alkyl/arylpyrroles 5 by their reaction with aminoacetaldehyde dimethylacetal followed by acid catalyzed cyclization in ethereal HCl. The reaction of 2 with propargyl alcohol has also been investigated

Preparation of lithium 5-lithiomethy-3-methylpyrazole-1-carboxylate and its reaction with α-oxoketene dithioacetals: a new general method for substituted and annelated pyrazolo[1,5-a]pyridines

5-Methylpyrazole derivative 1 is metallated at the C-5 methyl carbon atom to form lithium 5-lithiomethyl-3-methylpyrazole-1-carboxylate 3 which on reaction with α-oxoketene dithioacetals 4a-d, 12a-c and 15a-b yields substituted and annelated pyrazolo[1,5-a]pyridines 7a-d, 13a-c and 16a-b

Synthesis of novel 3-cyano-4-methylthio-6-(arylcyclopropyl)-3-(1H)-pyridones and 5(3)-methylthio-3(5)-(arylcyclopro-pyl)pyrazoles

1056-105

Heteroaromatic annulation studies on 2-[bis(methylthio)methylene]- 1-methyl-3-oxoindole: synthesis of novel heterocyclo[b] fused indoles

Heteroannulation of 2-[Bis(methylthio)methylene]-1-methyl-3-oxoindole with β- substituted β-lithioaminoacrylonitrile, malononitrile and guanidine has been reported to yield novel substituted pyrido[3,2-b]indoles and pyrimido[5,4-b]indole derivatives in varying yields

Reaction of ɑ-bis(methylthio)methylene cyclopropyl ketones with guanidine: Synthesis of 2-amino-4-alkoxy-6-(ary1cyclopropyl)pyrimidines

1123-112

Synthesis of novel 3-arylcyclopenta[c]quinolines via acid-induced domino cyclization of 2-arylamino-2-methylthioethenyl 2-arylcyclopropyl ketones

A novel acid-induced domino cyclization of N,S-anilinoacetals of type 3 derived from 2- arylcyclopropyl ketones, is reported which yields a wide range of substituted- and fused- 3- arylcyclopenta[c]quinolines 6 with concomitant formation of a cyclopentane and a quinoline ring

α-Oxoketene dithioacetals as intermediates for aromatic annelation

The α-oxoketene dithioacetals of general formula 1 (Scheme 2), undergo regioselective 1,2-addition with allyl anions to afford the corresponding carbinol acetals 6 in quantitative yields, which on treatment with BF3.Et2O in refluxing benzene yield the corresponding aromatic systems. The method has been shown to be widely applicable as exemplified by a large number of allyl anions (Scheme 3) reacting with agr-oxoketene dithioacetals with wide structural variation. However, when 1 carry the agr-substituent the intermediate carbinol acetals 14 (Scheme 4) follow, different path to yield the corresponding indenes 15 in good yields. The cinnamoylketene dithioacetals 16 react with allyl anions to afford the corresponding methylthiostilbenes 18 (Scheme 5), while the homologous dithioacetal 20 failed to yield the corresponding 1,4-biaryl-1,3-diene 22 (Scheme 6). This limitation was circumvented by reacting 23 with allyl anions to afford the corresponding stilbenes 24, dienes 25 and triene 26 respectively. The method was successfully extended for naphthoannelation. Thus naphthalenes 28 (Scheme 7) were prepared by reacting benzylmagnesium chloride with 1. In this case the reaction followed a sequential 1,4-and 1,2-addition mode and yielded the corresponding benzyl substituted naphthalenes. This problem was solved by reacting benzylmagnesium chloride with 8 to afford the corresponding naphthalenes 31 (Scheme 8) in excellent yields. Similarly the lithio derivatives derived from toluene followed 1,2-addition mode with 1 to afford the derived methylthionaphthalenes 39 (Scheme 9) in high yields. The other alkyl substituted naphthalenes 41,43 (Scheme 9), 45,47 (Scheme 10) were similarly prepared. Also 1 and β-oxodithioacetals 8 reacted with 1-naphthylmethylmagnesium chloride to afford the corresponding phenanthrenes 49 and 51 respectively in good yields. The method was extended to benzanthracene 56 (Scheme 11) synthesis successfully. The 2-naphthylmethyl magnesium chloride reacted in a sequential 1,4- and 1,2- fashion to afford the corresponding naphthylmethyl hydrocarbons 58 while it reacted with β-oxodithioacetals to give expected condensed aromatics 60, 61 and 62 (Scheme 12) in high yields. The 1-naphthylmethylmagnesium chloride also reacted with β-oxodithioacetals 23 to afford the corresponding styrylphenanthrenes 65, dienes 66 and triene 67 respectively in high yields. The intermediate 69 precursor in the synthesis of hexahelicine was also obtained by reacting 68 with 1-naphthylmethylmagnesium chloride (Scheme 13). The oxygenated benzylmagnesium halides reacted with 1 in 1,2-fashion (Scheme 14) with the exception of the formation of 79. Five fold excess of Reformatsky reagent reacted with 1 to afford the corresponding salicylates 82 (Scheme 15) in high yields. Similarly 84 (Scheme 16) was formed. Propargylmagnesium chloride also reacted with 1 with the participation of solvent methanol to afford the corresponding thioresorcinol dimethylethers 86 (Scheme 17) in high yields. However, intermolecular solvent participation did not occur with open chain agr-oxoketene dithioacetals (Scheme 18) and the possible mechanism for this transformation is proposed (Scheme 19). The anion derived from aminocrotonate 97 (Scheme 20) reacted with 1 to afford the corresponding aminosubstituted aromatics 100. To prepare totally unsubstituted aromatics the allylanion was reacted with phenylthioacrolein 101 as exemplified by the synthesis of benzene 108a (Scheme 23), naphthalenes 109,110 and phenanthrene 111 (Scheme 24). In general our new method of aromatic annelation is a versatile, efficient and widely applicable for creating a large number of aromatics from easily accessible open chain precursors

A novel route to 2-alkoxy / aryloxythiophenes via Simmons-Smith reaction on acylketene O,S-acetals

A novel route to 2-alkoxy/aryloxy-4-arylthiophenes 4a-k and the corresponding 3,4-annulated thiophene 7 has been developed by subjecting the respective acylketene O,S-acetals 1a-k and 6 to Simmons-Smith reaction conditions (zinc-copper/diiodomethane)