Synthesis of Pentasubstituted Pyridines. IV—Structural Characterization of the Addition Products of 1-(N,N-Diethylamine)prop-1-yne toN-Vinylcarbodiimides and -ketenimines
The reaction products of the addition of 1‐(N,N‐diethylamine)prop‐1‐yne toN‐vinylcarbodiimides and ‐ketenimines have been identified. Two pyridine regioisomers can be obtained under thermal control according to a [4+2] or [2+2] cycloaddition mechanism. At temperatures above 100°C a competingelectrocyclic ring closure of the heterocumulene is observed. The structures of the pyridines isolated are assigned
1-(N,N-二乙胺)丙-1-炔与N-乙烯基碳二亚胺和-烯酮亚胺的加成反应产物已被鉴定。根据[4+2]或[2+2]环加成机理,在热控制下可以获得两种吡啶区域异构体。在高于 100°C 的温度下,观察到杂枯草烯的竞争性电环闭合。分离的吡啶的结构由 HMBC 和 NOE 差异光谱的组合指定。