Acyl-substituted thiocarbonyl ylides

Acyl-substituted thiocarbonyl ylides have been suggested to undergo 1,5-dipolar cyclization to give 1,3-oxathioles (55,179-183). Convincing evidence for the intermediacy of thiocarbonyl ylide 146 involves the formation of structure 147 starting from either two different pairs of reagents (179,180) (Scheme 5.44). 

When thiocarbonyl and ot-diazocarbonyl compounds are combined, acyl-substituted thiocarbonyl ylides 158 are generated from a nonisolable 3-acyl-1,2,4-thiadiazoline 157 (Scheme 8.36). In addition to giving acylthiiranes 159 and 1,3-dithiolanes 160, dipoles 158 can also 1,5-cyclize to produce 1,3-oxathioles 161. Acyl-thiocarbonyl ylides derived from diazoketones [e.g., HC(0)C(N2)R, R = Ph, f-Bu (219,220) 2-diazocyclohexanone (221)] produce 1,3-oxathioles [e.g., 162 (220), Scheme 8.36], while those derived from diazoesters (218,222,223) lead to thiiranes by 1,3-cyclization. Ylides derived from a-diazocarboxamides form 1,3-oxathioles (e.g., 163) and thiiranes (e.g., 159, R = f-Bu, R = NMePh, R = R" = Ph), depending on the nature of the substituents (220). A related 1,5-cyclization of an aminomethyl-thiocarbonyl ylide formed from dimethyl 3-anilino-2-diazobutanedioate was also reported (224). 

Geometrical trans to cis isomerization of 3,3 -, 4,4 -, and 5,5 -disubstituted 2,2 -diphenoquinones has been studied by computational methods.The double bond isomerization of butene-catalysed l-ethyl-3-methyl-imidazolium chloride ionic liquid has been similarly examined and stepwise isomerization is suggested.The reaction of l,2-di(l-adamantyl)-2-thioxoethanone with diazomethane and 2-diazopropane gave 2-acylthiiranes via 2 - - 3-cycloaddition, elimination of nitrogen, and 1,3-dipolar electrocyclization of the intermediate acyl-substituted thiocarbonyl ylides. Rearrangement of pyrimidine-5-carboxylic acids esters to 5-acylpyrimidones does not occur in the examples studied and a [l,4]-phospho-Fries rearrangement has been reported. ... 

The synthesis of ylides which are a-substitued with a derivative of the caiboxy group can also be achieved via the addition of simple ylides to heteroallenes. The reaction with carbon oxysulfide gives rise to the formation of betaines from which alkylthiocarbonylalkylidenephosphoranes may be generated by alkylation and subsequent deprotonation (equation 78 X = O, Y = S). Carbon disulfrde reacts in a similar way yielding (alkylthio)thiocarbonyl-substituted ylides (equation 78 X = S, Y = S). These compounds are also available from the reaction of simple ylides with trithiocarbonates or dithiochloro-carbonates in analogy to the acylation of ylides (see equations 71 and 72). ... 

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