title: Sequential one-pot InBr(3)-catalyzed 1,4- then 1,2-nucleophilic addition to enones.
abstract: Low sensitivity toward traces of moisture and high tolerance of different functional groups make indium tribromide suitable for carrying out multistep synthetic sequences. In particular, we have realized a 1,4-conjugated addition of indoles/thiols to alpha,beta-unsaturated ketones mediated by a catalytic amount (10 mol %) of InBr(3) obtaining the desired beta-substituted ketones in good yields. The Lewis acidity of indium salts was not affected by coordinating and acid nucleophiles; therefore, the subsequent catalytic 1,2-addition of Me(3)SiCN to carbonyl compounds can be performed in one pot. With the optimized atom-efficient protocol, several polyfunctionalized alpha-silyloxy cyanohydrins were synthesized in good to excellent yields (up to 97%) and a notable level of simple 1,3-diastereoselection (up to 84:16) was recorded in the case of 2-cyclohexen-1-one 2c.
authors.affiliation: Dipartimento di Chimica G. Ciamician, Università degli Studi di Bologna, via Selmi 2, 40126 Bologna, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Bandini
authors.forename: Pier Giorgio
authors.initials: PG
authors.lastname: Cozzi
authors.forename: Massimo
authors.initials: M
authors.lastname: Giacomini
authors.forename: Paolo
authors.initials: P
authors.lastname: Melchiorre
authors.forename: Simona
authors.initials: S
authors.lastname: Selva
authors.forename: Achille
authors.initials: A
authors.lastname: Umani-Ronchi