A simple two steps ytterbium triflate-catalysed preparation of 2,2-dimethyl-2h-chromenes from salicylaldehydes and 2-methylpropene

✍ Scribed by Soizic Prado; Yves L. Janin; Pierre-Etienne Bost

• Book ID: 102338224
• Publisher: Journal of Heterocyclic Chemistry
• Year: 2006
• Tongue: English
• Weight: 221 KB
• Volume: 43
• Category: Article
• ISSN: 0022-152X
• DOI: 10.1002/jhet.5570430626

✦ Synopsis

Abstract

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The preparation of various 2,2‐dimethyl‐2__H__‐chromenes was achieved in two steps via an ytterbium triflate‐catalysed reaction between salicylaldehydes, trimethylorthoformate and 2‐methylpropene. From salicylaldehyde, two reaction products were characterised: 4‐methoxy‐2,2‐dimethylchroman and 2‐(1,3‐dimethoxy‐3‐methylbutyl)phenol. The former compound probably results from a Lewis acid‐catalysed [2+4] cycloaddition between the intermediate quinonemethide and 2‐methylpropene whereas the latter may occur via a reaction related to a carbonyl‐ene reaction between the quinonemethide and 2‐methylpropene. Both compounds were subjected to a catalytic acidic treatment leading to 2,2‐dimethyl‐2__H__‐chromene. Starting from various salicylaldehydes, the scope of this method was investigated.