Kulkarni MG, Desai MP, Birhade DR, Shaikh YB, Dhatrak AN, Gannimani R. A Wittig-olefination-Claisen-rearrangement approach to the 3-methylquinoline-4-carbaldehyde synthesis.
Beilstein J Org Chem 2012;
8:1725-9. [PMID:
23209506 PMCID:
PMC3511006 DOI:
10.3762/bjoc.8.197]
[Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2012] [Accepted: 09/06/2012] [Indexed: 11/24/2022] Open
Abstract
Efficient syntheses are described for the synthetically important 3-methylquinoline-4-carbaldehydes 6a–h from o-nitrobenzaldehydes 1a–h employing a Wittig-olefination–Claisen-rearrangement protocol. The Wittig reaction of o-nitrobenzaldehydes with crotyloxymethylene triphenylphosphorane afforded crotyl vinyl ethers 2a–h, which on heating under reflux in xylene underwent Claisen rearrangement to give 4-pentenals 3a–h. Protection of the aldehyde group of the 4-pentenals as acetals 4a–h and subsequent oxidative cleavage of the terminal olefin furnished nitroaldehydes 5a–h. Reductive cyclization of these nitroaldehydes yielded the required 3-methylquinoline-4-carbaldehydes 6a–h in excellent yields. Therefore, an efficient method was developed for the preparation of 3-methylquinoline-4-carbaldehydes from o-nitrobenzaldehydes in a simple five-step procedure.
Collapse