Abstract
The N-heterocyclic carbene catalyzed (4 + 2) cycloaddition between alpha,/beta-unsaturated acid fluorides and TMS dienol ethers provides cyclohexene fused beta-lactone intermediates stable below -20 degrees C. These can be intercepted reductively or with organolithium reagents to produce diastereomerically pure cyclohexenes (>20:1 dr) with up to four contiguous stereocenters. The mechanism has been investigated using theoretical calculations and by examining secondary kinetic isotope effects. Together these studies implicate the formation of a diastereomerically pure beta-lactone intermediate by a stepwise (4 + 2) cycloaddition involving Michael addition, aldol cyclization, and lactonization.
Original language | English |
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Pages (from-to) | 1113 - 1124 |
Number of pages | 12 |
Journal | The Journal of Organic Chemistry |
Volume | 77 |
Issue number | 2 |
DOIs | |
Publication status | Published - 2012 |