Methylaluminum bis(4-substituted-2,6-di-tert-butylphenoxide) as an efficient nonchelating Lewis acid: Application to asymmetric Diels-Alder reaction and diastereoselective alkylation to alkoxy carbonyl substrates
The exceptionally bulky methylaluminum bis(4-substituted-2,6-di-tert-butylphenoxide) such as MAD or MABR can be successfully utilized as a highly efficient nonchelating Lewis acid for achieving high stereoselectivity in 1,n asymmetric induction in cyclic as well as acyclic systems. Thus, Diels-Alder reaction of the acrylate of D-pantolactone and cyclopentadiene in the presence of such bulky organoaluminum