Nucleophilic reaction of fluoroolefins. V. Regioselectivity and stereochemistry in the reactios of 1-phenylpentafluoropropenes with lithium dialkylamides

1-Phenylpentafluoropropenes $\text{1}$ readily react with lithium dialkylamides to give, in most cases, mixtures of 1-aminosubstituted alkenes $\text{2}$ and 2-amino-substituted alkenes $\text{3}$, with the latter being the favoured products. The reactions with bulky lithium diethylamide and lithium 2-methylpiperidinoamide gave exclusively 1-amino-substituted products $\text{2}$. The effect of the increased bulk of N-nucleophiles is opposite to that observed for the reactions of alkenes $\text{1}$ with C-nucleophiles Increasing electronegativity of the phenyl ring substituents in alkenes $\text{1}$ shifts the regioselectivity of the attack of lithium amides towards the C2 carbon atom. The E to Z isomer ratios of enamines $\text{2}$ were found to be time dependent and the slow isomerisation of the kinetic isomers E to the thermodynamic isomers Z was observed, while the ratio of isomers of enamines $\text{3}$ did not change with time.A concerted, single-step process is suggested for the reactions of alkenes $\text{1}$ with lithium dialkylamides, and a tentative explanation of the different stereochemistry of enamines $\text{2}$ and $\text{3}$ is given.