Recent Publications
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RZnI vs R2Zn in Pd(0)-Catalyzed Cross-Coupling Reactions With Thioimidates Canadian Journal of Chemistry, 2003, in press.
Thioimidates 1-Z undergo facile cross-coupling with Pd(0)/RZnI but are inert to Pd(0)/R2Zn. This difference is due to the lower Lewis acidity of R2Zn as opposed to lower nucleophilicity. Various sources of RZnI (R = Me, Et) and Pd(0) were evaluated for their convenience and reactivity
On the Methylation of Carboxyl Groups with Methanesulfonyl Chloride in Pyridine. Synthetic Communications 2003, 33, 2575.
Enantioselective Syntheses of Ring-C Precursors of Vitamin B12. Substrate Control. A Novel Si-Assisted Elimination of Vinyl Bromides Org. Lett. 2003 5, 4879.
Homochiral ring-C precursors 34 of Vitamin B12 have been prepared by Ireland-Claisen rearrangement of allyl esters 32, followed by a novel Si-assisted elimination of HBr.
Enantioselective Syntheses of Ring C Precursors of Vitamin B12. Reagent Control. Org. Lett. 2003, 5, 701.
Enelactones of general structure S-(-)-I were prepared in three steps from alcohol 21 and acids 22 (ee~85%). Lactones S-(-)-I are versatile precursors to enelactams II of the type found in Vitamin B12.
Lewis Acid-Promoted Oxidative Addition of Thioimidates to Pd(0) J. Org. Chem. 2002, 67, 9304.
The isomeric S-methyldihydropyrrins 9-Z and 9-E exhibit markedly different behavior in Pd(0)-catalyzed cross-coupling reactions. Thioimidates 9-Z are readily converted to imines 10-Z employing Pd(0)/AlkZnI. Under identical conditions 9-E are inert. Oxidative addition to Pd(0) requires activation by Zn or other Lewis acids, which is sterically unfavorable with 9-E. Analogous results were obtained with the related thioimidates 11-E,Z as well as with methylthiopyridines 19-. In the case of both 11 and 19 oxidative addition to Pd(0) was greatly facilitated in the presence of BF3·Et2O. The importance of Lewis acid activation to Pd(0) oxidative addition in such substrates appears to be a general phenomenon not previously recognized.