186790-02-3Relevant academic research and scientific papers
Diverse reactions of 1,4-dilithio-1,3-dienes with nitrites: Facile access to tricyclic Δ1-bipyrrolines, multiply substituted pyridines, siloles, and (Z,Z)-dienylsilanes by tuning of substituents on the butadienyl skeleton
Yu, Nan,Wang, Congyang,Zhao, Fei,Liu, Lantao,Zhang, Wen-Xiong,Xi, Zhenfeng
experimental part, p. 5670 - 5679 (2009/05/28)
Addition cyclization of 1,2,3,4-tetrasubstituted 1,4-dilithio-1,3-dienes (Type I) with four equivalents of various aromatic nitriles in the presence of hexamethylphosphoramide (HMPA) gives exclusively fully substituted pyridines in moderate to good yields. Similarly, trisubstituted pyridines can be prepared by the reaction of 2,3-dialkyl- or diaryl-substituted 1,4dilithio-1,3-dienes (Type II) with nitriles. However, five- or six-memberedring fused 2,3-disubstituted 1,4-dilithio1,3-dienes (Type III) reacted with various aromatic and aliphatic nitriles without a-hydrogen atoms to afford tricyclic Δ1- bipyrrolines in high yields. The reaction of six-membered-ring fused 2,3-disubstituted 1,4-dilithio-1,3-diene (Type III) with 2-cyanopyridine afforded the corresponding pyridine, and no tricyclic Δ1- bipyrroline was observed. Seven-membered-ring fused dilithiodienes reacted with PhCN or trimethylacetonitrile to afford the corresponding pyridines in good yield. When 1,2,3,4-tetrasubstituted dilithio reagents (Type I) were treated with Me3SiCN, a tandem silylation/intramolecular substitution process readily occurred to yield siloles, whereas the reaction of 2,3-disubstituted dilithio reagents (Types II and III) with Me3SiCN gave rise to (Z,Z)-dienylsilanes with high stereoselectivity. These results revealed that the formation of tricyclic Δ1-bipyrrolines, pyridines, siloles, and (Z,Z)-dienylsilanes are strongly dependent on the substitution patterns of the dilithio butadienes and the nature of the nitriles employed.
