Lewis Add-catalyzed Additions

The real promise of this catalytic reaction is the eventual development of an efficient enantioselective aUylboration catalyzed by chiral Lewis acids. Currently, the on- 

Rgure 6.6 Possible transition structures tor the Lewis acid-catalyzed aUylboration. (A) Coordination of a boronate oxygen. (B) Double coordination of the aldehyde carbonyl. 

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Subsequently, a large number of methods have been developed for the preparation of optically active a-aminophosphonates nucleophilic addition of lithium dibenzyl phosphonate to the spironitrone [26] Lewis add-catalyzed addition of diethyl H-phosphonate to A -galactosyUmine [27] addition of lithium diethyl phosphonate to chiral chelating imines [28]. 

Several reviews on allylboron compoimds and odier allylmetal reagents and their additions to carbonyl compoimds and imines have appeared [1-6], including two excellent chapters in a book from Wiley-VCH [1,2]. Accordingly, diis chapter does not aim to provide a comprehensive accoimt on die chemistry of allylboronates, but presents instead an overview of die main preparative methods for allylboronates, with particular focus on advances reported in die past five years, and on several recent synthetic applications such as the Lewis add-catalyzed additions to carbonyl compounds and tandem allylation reactions. 

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