Lithiated enol carbamates

Lithiated enol carbamates 559 have been reported as complementary acyl anion equivalents of MVL (524) and EVL (525). Non-fluorinated enol carbamates have been prepared by O-carbamoylation of acetaldehyde lithium enolate (80-87% yield) or by quantitative addition of trimethylsilylamides to vinyl chloroformate837. 

The stabilization by a heteroatom of the lithiated enolate can be realized by using carbamates and methylmethoxyethers (MEM) of trifluoroethanol. As shown in Figure 2.19, these enolates are powerful tools for the synthesis of difluorocompounds, especially to access difluorosugars. ... 

Lithiated di- and monofluorinated enol carbamates 566844 847 and 567848 are fluorine-containing acyl anion equivalents, which allow the synthesis of a-fluorinated ketones. 

The lithiation of an O-vinyl carbamate with rAr-BuLi followed by transmetallation with zinc bromide provides the convenient acyl anion derivative, which undergoes smooth Pd(0)-catalyzed cross-coupling reactions (Equation (24)).67 This reaction sequence has been extended to lithium enolates. The deprotonation of the aminoester with LDA followed by a transmetallation with zinc bromide in ether furnishes a zinc enolate, which readily adds to the double... 

V-Boc allylic amines are readily obtained by CuCN-mediated coupling of enol triflates with the a-lithiated carbamates. This method offers regio- and stereocontrol with respect to the double bond. However, it cannot be extended to the preparation of benzylamine derivatives. 

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