Ritter Reactions. XIII Reactivity of Methyl Schiff Bases with Dimethyl Acetylenedicarboxylate and Mercaptoacetic Acid

Abstract

Reactions of several methyl imines with dimethyl acetylenedicarboxylate and with mercaptoacetic acid have been studied to investigate further the capricious behaviour of this functionality. The 1 : 1 adduct of imine (1) and dimethyl acetylenedicarboxylate is confirmed as the pyrroloisoquinoline structure (7) by X-ray methods [C₁₇H₁₇NO₅, P ^-1, a 9·037(2), b 9·276(2), c 10·033(2) Å, α 81·99(1), β 81·28(1), γ 64·9(2)°, Z 2, R 0·044]. New products from (2) and dimethyl acetylenedicarboxylate, the 1 : 1 adduct (10) which is readily converted into the known product (9), and the 1 : 2 adduct (12), are described. The structure of the last compound, which arises through a rearrangement process, was determined by X-ray crystallography [C₂₇H₃₆N₂O₉,P ca2₁, a 19· 083(4), b 15·217(3), c 9·669(2) Å, Z 4, R 0·038]. Methyl imines (1) and (4) undergo cyclocondensation with mercaptoacetic acid yielding thiazolidinone products but others are inert under similar conditions.