Modulating NHC catalysis with fluorine

作者：Rey Yannick P; Gilmour Ryan^*

来源：Beilstein Journal of Organic Chemistry, 2013, 9: 2812-2820.

DOI：10.3762/bjoc.9.316

• catalysis
• enantioselectivity
• fluorine
• gauche effect
• organo
• fluorine
• Steglich rearrangement

Fluorination often confers a range of advantages in modulating the conformation and reactivity of small molecule organocatalysts. By strategically introducing fluorine substituents, as part of a beta-fluoroamine motif, in a triazolium pre-catalyst, it was possible to modulate the behaviour of the corresponding N-heterocyclic carbene (NHC) with minimal steric alterations to the catalyst core. In this study, the effect of hydrogen to fluorine substitution was evaluated as part of a molecular editing study. X-ray crystallographic analyses of a number of derivatives are presented and the conformations are discussed. Upon deprotonation, the fluorinated triazolium salts generate catalytically active N-heterocyclic carbenes, which can then participate in the enantioselective Steglich rearrangement of oxazolyl carbonates to C-carboxyazlactones (e.r. up to 87.0: 13.0).

• 出版日期2013-12-6