Products from dimethyl hex-2-en-1-yne-1,6-dioate and dimethyl penta-2,3-diene-1,5-dioate with compounds possessing two adjacent nucleophilic centres

Abstract

Thioureas and thioamides were found to add via sulphur mainly to position 5 of dimethyl hex-2-en-4-yne-1,6-dioate; often this was followed by cyclisation to give γ-lactams. In some cases cis-addition was observed as well as trans-addition, even in methanol. Imidazoline-2-thione and benzimidazole-2-thione also reacted at position 4 to give fused thiazinone derivatives. 2-Amino-benzothiazole, -thiazole, and -pyridine all added via the ring nitrogen to position 4, and subsequent cyclisation gave fused pyrimidones. 1,2-Diaminobenzene and 2-aminobenzenethiol reacted like the thioureas at position 5, but addition to position 4 was followed by a further Michael addition to position 3. These benzene derivatives reacted with dimethyl penta-2,3-diene-1,5-dioate to give cyclic compounds with exocyclic unsaturated ester groups. In contrast, thioureas reacted with the allene to give derivatives of methyl 4-oxothiazin-6-ylacetate. Structures of the new compounds were deduced from their ¹H and ¹³C n.m.r., u.v., i.r., and mass spectra.