Lithioallyl carbamate

The regioselectivity in the reaction of enantioenriched lithioallyl carbamates with chlorotributyl- or chlorotrimethyltin depends largely on the substitution pattern of the alkenyl residue. Those derived from primary 2-alkenyl carbamates 302 provide exclusively or with large excess the 1-substitution products 313 with inversion of the configuration (equation No (E)-ent-314 was observed. 

It should be added here, that the 2,3-bond in ( )- and (Z)-lithioallyl carbamates is configurationally stable at the reaction temperature [174]. The y-silyl derivatives are a notable exception. Even when performing the deprotonation with a (Z)-3-trimethylsilyl-2-propenyl carbamate, after few minutes at -78°C, all of the material had been transformed to the lithiated (E)-isomer [175]. 

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