Diastereoselective Conjugate Addition of α-Lithiodithioacetals to the α,β-Unsaturated Lactam Unit of 5,6-Dihydropyrrolo[2,1-a]isoquinolinones

Begoña Etxarri; Inés González-Temprano; Izaskun Manteca; Nuria Sotomayor; Esther Lete

doi:10.1055/s-1999-2849

Synlett 1999; 1999(9): 1486-1488
DOI: 10.1055/s-1999-2849

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Diastereoselective Conjugate Addition of α-Lithiodithioacetals to the α,β-Unsaturated Lactam Unit of 5,6-Dihydropyrrolo[2,1-a]isoquinolinones

Begoña Etxarri^* , Inés González-Temprano, Izaskun Manteca, Nuria Sotomayor, Esther Lete

^*Departamento de Química Orgánica, Facultad de Ciencias, Universidad del País Vasco, Apdo. 644-48080 Bilbao, Spain; Fax + 34-94-4 64 85 00; E-mail: qopleexe@lg.ehu.es

Abstract

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Diastereoselective conjugate addition of α-lithiodithioacetals to α,β-unsaturated bicyclic lactams is described. Typical yields of the resulting tetrahydropyrrolo[2,1-a]isoquinolinones ranged 60-90% with facial diasteeoselectivities of > 95 : 5, when there is a bulky butyl group at the α-position to the nitrogen atom. Cis or trans isomers could be obtained exclusively by using 1,3-dithianyllithium or bis(phenylthio)methyllithium as nucleophiles, respectively. The presence of a methyl group at the 10b position of the heterocyclic system diminished the stereoselectivity. In selected diastereomeric byciclic lactams the acyl group was unmasked.

pyrroloisoquinolines - lactams - conjugated addition - lithium dithioacetals - diastereoselectivity

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