Highly efficient 1,7-asymmetric induction was achieved in DIBAL-H reduction and Grignard reaction of y-keto esters of podand-type l,l'-binaphthalen-2-ol derivatives bearing an appropriate oligoether group as the 2'-substituent. Thus, the DIBAL-H reduction of keto esters 4 in dichloromethane-toluene at -78 °C in the presence of an excess of MgBr2'OEt2 afforded, after further reduction of the resulting diastereomeric hydroxy esters, 1,4-diol 8 with up to 92% optical yield. A similar treatment of keto esters 4,5 and 7 with Grignard reagents gave the corresponding 4,4-disubstituted butan-4-olides 10-13 with up to 99% optical yield. The complexation experiments of keto ester 4b suggested that the highly efficient 1,7-asymmetric induction originated from the formation of a pseudo-macrocyclic magnesium complex composed of the podand keto ester and MgBr2.
|Number of pages||10|
|Journal||Journal of the Chemical Society, Perkin Transactions 1|
|Publication status||Published - 1999|