A Straightforward Access to Trifluoromethylated Spirobipyrazolines through a Double (3+2)-Cycloaddition of Fluorinated Nitrile Imines with Alkoxyallenes

Dedicated to Professor Janusz Zakrzewski (University of Łódź) on the occasion of his 70^th birthday

Abstract

Formal double (3+2)-cycloaddition of in situ generated tri­fluoroacetonitrile imines with alkoxyallenes proceeds in a highly regio- and diastereoselective manner to afford anti-configured spirobipyrazolines as the exclusive 2:1 adducts. Initial stepwise addition of the title electron-deficient 1,3-dipoles onto cumulenic reaction partner is pos­tulated to explain the observed reaction pathway.

Key words

nitrile imines - alkoxyallenes - (3+2)-cyclo­addition - pyrazolines - spiro compounds

• References and Notes


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