Design of chiral boronate-substituted acrylanilides. Self-activation and boron-transmitted 1,8-stereoinduction in [4+2] cycloaddition
The [4+2] cycloaddition of ortho-boronoanilide dienophile 4 with cyclopentadiene was found to proceed faster than both its para isomer 8 and the unsubstituted derivative 6, thereby confirming that self-activation by internal coordination is operative in the case of 4. Chiral boronic esters derivatives 9-13 provided a small level of remote 1,8-stereoinduction transmitted through a putative tetrahedral stereogenic boronate complex. These results show that dialkoxyboronic esters can operate as weak, internal Lewis acids and activate carbonyl-containing functionalities in cycloaddition reactions.
Kennedy, Jason W.J.,Hall, Dennis G.
p. 263 - 270
(2007/10/03)
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