title: Regioselective Synthesis of C-3-Functionalized Quinolines via Hetero-Diels-Alder Cycloaddition of Azadienes with Terminal Alkynes.
abstract: A highly efficient metal and protection-free approach for the regioselective synthesis of C-3-functionalized quinolines from azadienes (in situ generated from 2-aminobenzyl alcohol) and terminal alkynes through [4 + 2] cycloaddition has been developed. An unprecedented reaction of 2-aminobenzyl alcohol with 1,3- and 1,4-diethynylbenzene provided the C-3 tolylquinolines via [4 + 2] HDA and oxidative decarboxylation. The -NH2 group directed mechanistic approach was well supported by the control experiments and deuterium-labeling studies and by isolating the azadiene intermediate. The reactivity and selectivity of unprotected azadiene in metal-free base-assisted hetero-Diels-Alder reaction is exploited to quickly assemble an important class of C-3-functionalized quinolines, which are difficult to access.
authors.affiliation: Synthetic Organic Chemistry Research Laboratory, Department of Chemistry, University of Delhi , Delhi 110007, India.
authors.forename: Rakesh K
authors.initials: RK
authors.lastname: Saunthwal
authors.affiliation: Synthetic Organic Chemistry Research Laboratory, Department of Chemistry, University of Delhi , Delhi 110007, India.
authors.forename: Monika
authors.initials: M
authors.lastname: Patel
authors.affiliation: Synthetic Organic Chemistry Research Laboratory, Department of Chemistry, University of Delhi , Delhi 110007, India.
authors.forename: Akhilesh K
authors.initials: AK
authors.lastname: Verma