Asymmetric and nonasymmetric addition of RLi and RMgX to 3-methoxynaphthalen-2-yl oxazolines and imines. An approach to substituted 2-tetralones

Chiral and achiral 3-methoxynaphthalen-2-yl oxazolines 4a,b failed to under go an aromatic nucleophilic displacement of the 3-methoxy group with organo lithium reagents and instead afforded dihydronaphthalenes 9 and 14 in 30-95 % yield. Dihydronaphthalenes 9 (racemic) and 14 (nonracemic) were easily co nverted into the corresponding aldehydes 15. Alternatively, aldehydes 15 we re prepared via tandem addition of Grignard reagents to imines 17 in 50-65% yield. Aldehydes 15 served as precursors to 3,3,4-trisubstituted 2-tetralo nes 16. Use of methyl chloroformate to trap the azaenolate derived from 17f and i-PrMgCl afforded, in 65% yield, a versatile synthetic intermediate 23 which may serve to access 4-alkyl-, 3,4-dialkyl-, 3,4-disubstituted and 3, 3,4-trisubstituted 2-tetralones with diverse substitution patterns.