Sequential Diastereoselective Addition of Allylic and Homoallylic Grignard Reagents to 2-Acyl-perhydro-1,3-benzoxazines and Ring-Closing Metathesis: an Asymmetric Route to Azepin-3-ol and Azocin-3-ol Derivatives
Chiral 2-acyl-3-allyl-substituted perhydrobenzoxazinesderivedfrom (–)-8-aminomenthol react with allyl or homoallyl Grignard reagents to provide the corresponding tertiary alcohols in very good yields and with excellent diastereoselectivities. The 1,8- and 1,9-azadienes prepared in this way participate in RCM reactions to give good yields of seven- and eight-membered nitrogen heterocycles. The yields