title: Synthesis of 4H-3,1-benzoxazines, quinazolin-2-ones, and quinoline-4-ones by palladium-catalyzed oxidative carbonylation of 2-ethynylaniline derivatives.
abstract: An effective and straightforward approach to the synthesis of 4H-3,1-benzoxazines 3 and 4, quinazolin-2-ones 5, and quinoline-4-one derivatives 6 and 7 is provided by palladium-catalyzed cyclization-alkoxycarbonylation of variously substituted 2-(trimethylsilanyl)ethynylaniline amide or urea derivatives 2. Reactions are carried out in 7:1 MeCN/MeOH at 65 or 75 degrees C in the presence of catalytic amounts of 10% Pd/C in conjunction with Bu(4)NI and KF and under 2.4 MPa of a 3:1 mixture of CO and air. Anti and syn 6-exo-dig cyclization modes account for the formation of the two stereoisomers. Isomerization of the vinylpalladium intermediate may occur as well. Formation of a double carbonylation product 7r and of a gem-dimethoxycarbonylation product 6s, whose structures have been determined by X-ray diffraction analysis, is justified through an unusual type of rearrangement.
authors.affiliation: Dipartimento di Chimica Organica e Industriale, Università di Parma, Parco Area delle Scienze 17/A, 43100 Parma, Italy. mirco.costa@unipr.it
authors.forename: Mirco
authors.initials: M
authors.lastname: Costa
authors.forename: Nicola Della
authors.initials: ND
authors.lastname: Cà
authors.forename: Bartolo
authors.initials: B
authors.lastname: Gabriele
authors.forename: Chiara
authors.initials: C
authors.lastname: Massera
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Salerno
authors.forename: Matteo
authors.initials: M
authors.lastname: Soliani