The 1,3-Dipolar Cycloaddition Reactions of Heteroaromatic Dicyanomethylides with Phenylsulfinylethene and Bis(trimethylsilyl)ethyne: Synthesis of 1,2-Unsubstituted 3-Cyanoindolizines
Pyridinium and diazinium dicyanomethylides underwent 1,3-dipolar cycloaddition-extrusion reactions with phenylsulfinylethene, producing the corresponding 3-cyanoindolizines in moderate to good yields. 1,3-Dipolar cycloadditions of these ylides with bis(trimethylsilyl)ethyne gave either the 1,2-bis(trimethylsilyl)-3-cyanoindolizines or the 1-trimethylsilyl-3-cyanoindolizines, or mixtures of these, depending
Reactions of indolizine-3-carbonitriles with dimethylacetylenedicarboxylate (DMAD), in the presence of Pd–C, gave the corresponding [2.2.3]cyclazines in low to moderate yields, whereas, in the absence of Pd–C, the same reactions afforded the 1 : 2 molar products. The X-ray analysis of one of the 1 : 2 adducts established that the structure was dimethyl 2-cyano-3-styrylpyrrole-1,4-dicarboxylate. A
Refluxing a mixture of 3-cyanoindolizine and dimethyl acetylenedicar☐ylate in toluene affords a 1:2 adduct, the structure of which is unambiguously determined by an X-ray analysis.