Preparation of Chiral 2-(2-Bromobenzyl)-1,3-dioxolanes and Their Addition to Acylimines

✍ Scribed by Bernhard Wünsch; Sven Nerdinger

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 587 KB
• Volume: 1998
• Category: Article
• ISSN: 1434-193X
• DOI: 10.1002/(sici)1099-0690(199804)1998:4<711::aid-ejoc711>3.0.co;2-a

✦ Synopsis

1,2,3,4-tetrahydroisoquinoline / NMDA antagonists A series of enantiomerically pure 2-(2-bromobenzyl)-1,3-dioxolanes 10 has been prepared by transacetalization of the dimethyl acetal 8 or the enol ether 7 with enantiomerically pure C 2 symmetric 1,2-diols. We investigated the ability of the chiral 1,3-dioxolane moiety to control the diastereoselectivity during the addition of the aryllithium intermediates 18 to the acylimines 17. Those reactive aryllithium species were generated by bromine/lithium exchange at the bromo acetals 10. In this series the best diastereoselectivity was obtained Scheme 1

We therefore planned to devise a novel asymmetric synthesis to obtain enantiomerically pure 1-aryl-1,2,3,4-tetrahydroisoquinolines. In contrast to the established asymmetric syntheses of 1-aryltetrahydroisoquinolines, which utilize complete isoquinoline ring systems for the introduction of [᭛] Part 1: Ref. [1] .