Silylium ion mediated 2+2 cycloaddition leads to 4+2 Diels-Alder reaction products.
Commun Chem 2020;
3:126. [PMID:
36703398 PMCID:
PMC9814679 DOI:
10.1038/s42004-020-00373-2]
[Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2020] [Accepted: 08/05/2020] [Indexed: 01/29/2023] Open
Abstract
The mechanism of silver(I) and copper(I) catalyzed cycloaddition between 1,2-diazines and siloxy alkynes remains controversial. Here we explore the mechanism of this reaction with density functional theory. Our calculations show that the reaction takes place through a metal (Ag+, Cu+) catalyzed [2+2] cycloaddition pathway and the migration of a silylium ion [triisopropylsilyl ion (TIPS+)] further controls the reconstruction of four-member ring to give the final product. The lower barrier of this silylium ion mediated [2+2] cycloaddition mechanism (SMC) indicates that well-controlled [2+2] cycloaddition can obtain some poorly-accessible IEDDA (inverse-electron demand Diels-Alder reaction) products. Strong interaction of d10 metals (Ag+, Cu+) and alkenes activates the high acidity silylium ion (TIPS+) in situ. This п-acid (Ag+, Cu+) and hard acid (TIPS+) exchange scheme will be instructive in silylium ion chemistry. Our calculations not only provide a scheme to design IEDDA catalysts but also imply a concise way to synthesise 1,2-dinitrogen substituted cyclooctatetraenes (1,2-NCOTs).
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