Construction of Spiropyrido[2, 1‐ a ]isoquinoline via Tandem Reactions of Huisgen's 1,4‐Dipoles with Various Alkene Dipolarophiles

The three‐component reaction of isoquinoline, dimethyl acetylenedicarboxylate and arylidene pivaloylacetonitrile in acetonitrile at room temperature afforded pyrido[2, 1‐ a ]isoquinolines 1 a‐1 j in good yields and with high diastereoselectivity. When arylidene‐substituted 1,3‐indanediones, Meldrum acids, and N,N’ ‐dimethylbarbituric acids were employed in the reaction, the novel functionalized spiro[indene‐2, 1′‐pyrido[2, 1‐ a ]isoquinolines] 2 a‐2 j , spiro[pyrido[2, 1‐ a ]isoquinoline‐1,5′‐[1, 3]dioxanes] 3 a‐3 h and spiro[pyrido[2, 1‐ a ]isoquinoline‐1,5′‐pyrimidines] 4 a‐4 e were also efficiently synthesized in satisfactory yields. The reaction mechanism included domino formation of Huisgen's 1,4‐dipole, Michael addition and cyclization processes.