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A cascade double 1,4-addition/intramolecular annulation strategy for expeditious assembly of unsymmetrical

Xinwei He^1,2, Ruxue Li³, Pui Ying Choy⁴

¹Key Laboratory of Functional Molecular Solids, Ministry of Education, College of Chemistry and Materials Science, Anhui Normal University, Wuhu, 241000, PR China. xinweihe@mail.ahnu.edu.cn.

Communications Chemistry

|January 25, 2023

Abstract:

Existing synthetic routes for accessing dibenzofuran core have intrinsic regioselectivity, limiting the substitution patterns available in heteropolycyclic arene products. Here we report a double 1,4-conjugate addition/intramolecular annulation cascade reaction between propargylamines and two equivalents of imidazolium methylides that allows efficient access of structurally versatile dibenzofurans. This transition metal-free protocol proceeds smoothly under bench-top air atmosphere and offers easy manipulation of substituents on the dibenzofuran core, and also provides good-to-excellent product yields with good functional group tolerance, particularly the -Br and -Cl groups which are often incompatible with existing metal-catalyzed C-C and/or C-O bond ring-forming processes. It is worth noting that ladder-type π-systems with all-arene quarternary carbon structure can be straightforwardly generated upon simple late-stage functionalization.

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