Construction of Unique Spiro[dibenzo[<i>a</i>,<i>f</i>]azulene-6,2′-indenes] via Unprecedented Annulation of <i>ortho</i>-C–H Bond of Benzylidene Group
Yu‐Wei He, Wei-Qing Ma, Ying Han, Jing Sun, Chao‐Guo Yan
Abstract
The domino reaction of alkyl and aryl isocyanides with two molecules of 2-arylidene-1,3-indanediones in acetonitrile at 80 °C resulted in unique functionalized spiro[dibenzo[ a, f ]azulene-6,2′-indenes] in good yields, in which the two 2-arylidene-1,3-indanediones acted as different building blocks to construct the polycyclic system. More importantly, the unprecedented anticipation of the ortho-position of benzylidene group to form a novel dibenzo[ a, f ]azulene ring through a formal [5 + 2] cycloaddition process was first observed. On the other hand, DABCO-promoted reaction of the isocyanides with two molecules of 2-arylidene-1,3-indanediones in acetonitrile at 80 °C afforded functionalized spiro[cyclopenta[ a ]-indene-2,2′-indene] derivatives.