Synthesis of gem-difluoromethylenated analogues of boronolide

• Jing Lin,
• Xiao-Long Qiu and
• Feng-Ling Qing

Beilstein J. Org. Chem. 2010, 6, No. 37, doi:10.3762/bjoc.6.37

• , Shanghai 200032, China 10.3762/bjoc.6.37 Abstract The straightforward synthesis of four gem-difluoromethylenated analogues 4–7 of boronolide is described. The key steps of the synthesis include the concise preparation of the key intermediates 12a–b through the indium-mediated gem-difluoropropargylation of

• aldehyde 9 with the fluorine-containing building block 11 and the efficient construction of α,β-unsaturated-δ-lactones 15a–b via BAIB/TEMPO-procedure. Keywords: boronolide; gem-difluoromethylenated analogues; gem-difluoropropargylation; α,β-unsaturated-δ-lactones; Introduction (+)-Boronolide (1

• -containing intermediate 11 was accomplished from propargyl alcohol (10) by our improved procedure [22]. With these two key fragments in hand, we focused our efforts on the gem-difluoropropargylation reaction. Utilizing Hammond’s reaction conditions [25], we were pleased to find that treatment of aldehyde 9