title: A Wittig-olefination-Claisen-rearrangement approach to the 3-methylquinoline-4-carbaldehyde synthesis.
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.
authors.affiliation: Department of Chemistry, University of Pune, Ganeshkhind, Pune 411007, India;
authors.forename: Mukund G
authors.initials: MG
authors.lastname: Kulkarni
authors.forename: Mayur P
authors.initials: MP
authors.lastname: Desai
authors.forename: Deekshaputra R
authors.initials: DR
authors.lastname: Birhade
authors.forename: Yunus B
authors.initials: YB
authors.lastname: Shaikh
authors.forename: Ajit N
authors.initials: AN
authors.lastname: Dhatrak
authors.forename: Ramesh
authors.initials: R
authors.lastname: Gannimani