93272-44-7Relevant academic research and scientific papers
α-MONOHALOALKYLLITHIUMS NON FONCTIONNELS
Tarhouni, R.,Kirschleger, B.,Villieras, J.
, p. C1 - C4 (1984)
New stable monohalocarbenoids RCXLiCH3 (X = Cl, Br; R = H, CH3, alkyl) are prepared by bromine-lithium exchange from the corresponding bromohaloalkanes RCXBrCH3 and s-butyllithium in the presence of one equivalent of lithium bromide at -115 deg C in a mixture of THF/Et2O/pentane.These carbenoids are treated with carbonyl compounds and give epoxides at -90 deg C (X = Br).Epoxidation is activated by the presence of LiBr (electrophilic activation).
Proprietes nucleophiles des carbenoides monohalogenes non fonctionnels
Villieras, J.,Kirschleger, B.,Tarhouni, R.,Rambaud, M.
, p. 470 - 478 (2007/10/02)
The coupling of non functionalised monohalocarbenoids R1-CXLi-R2 1 (R1 = alkyl, H ; R2 = H, CH3) with carbonyl compounds at -115 degree leads to the formation of lithium salts of halohydrins which readily give epoxides (via lithium halide elimination) at -95 degree in the presence of lithium bromide.The regiospecific synthesis of α-haloketones and α-haloaldehydes can be achieved by acylation of 1 with esters.A total lack of reactivity of 1 towards powerful alkylating electrophiles has been observed showing that they are not nucleophilic organometallics.The reactivity with carbonyl compounds seems to be promoted by the carbonyl-lithium (from the carbenoid) complexation.A correlation between nucleophilic/electrophilic properties of carbenoids (mono-, di- and trihalo-) and their assigned structure (metallocarbenium halides) is discussed.
