Di‐ und trifluorsubstituierte Dilithium‐Verbindungen für die Organische Synthese

Abstract

Unerwartet stabil gegen Fluorid‐Eliminierung sind die Dilithium‐Derivate 1 sowie 1, F3HC, und 3 (≥90% ee, (R)‐Form). Sie können bei tiefen Temperaturen in Tetrahydrofuran erzeugt und mit Carbonylverbindungen bzw. Alkylierungsmitteln in Ausbeuten um 50% zu 2 (X=H,F) bzw. 4 umgesetzt werden.

Synthetic applications of the carbanion generated from 4,4,4-trifluorobutan-2-one

“…In particular, the stereoselective introduction of fluoromethyl groups onto the sequential carbon atoms has not been studied in detail. Moreover, the chemistry of b-fluorocarbanions, which do not undergo elimination to form fluoroolefins, has not been studied for the construction of regio-and stereocontrolled fluorinated materials [9][10][11][12][13], except for indium-mediated allylation [14]. Further, except for diastereoselective perfluoroalkylation of chiral N-acyloxazolidinones [15], no other examples of highly diastereocontrolled difluoromethylation [16] have been reported to our knowledge.…”

Stereocontrolled Synthesis of β-Difluoromethylated Materials

“…To date, synthetic strategies for the preparation of terminal difluoroolefins have been based on a few methods: (1) the lithiation of 1,1-difluoroethene and trapping of the intermediate with CO 2 , (2) the decarboxylation of bromodifluoromethylated malonate, (3) the dehydrofluorination of trifluorinated isobutyrate, and (4) the Wittig difluoromethylation of pyruvate . Moreover, the chemistry of terminal difluoroolefins, which do not undergo elimination to form fluoroolefins, has not been studied for the construction of regio- and stereocontrolled fluorinated materials, − except for indium-mediated allylation . Clearly, development of selective and/or specific synthetic methods for geometorical isomers and/or optically active β-difluoromethyl esters and/or acids remains an important synthetic challenge.…”