A mild method for the replacement of a hydroxyl group by halogen: 3. the dichotomous behavior of α-haloenamines towards allylic and propargylic alcohols
A study of the deoxyhalogenation of allylic and propargylic alcohols with tetramethyl-α-halo-enamines is reported. Primary allylic and primary and secondary propargylic alcohols gave the corresponding halides in high yields. Secondary allylic and propargylic alcohols yielded the corresponding secondary halides but the reaction also produced some rearranged primary halides (I > Br > Cl). The reactions with tertiary allylic and tertiary propargylic alcohols gave several products and was therefore of little synthetic value. However, the addition of triethylamine to the reaction mixture or the use of lithium alkoxide instead of alcohol brought about a major change of the course of the reaction which led to amides carrying an allyl or an allenyl group at C2. This was shown to result from a Claisen-Eschenmoser rearrangement of an intermediate α-allyloxy- or propargyloxy-enamine.
Munyemana, Fran?ois,Patiny, Luc,Ghosez, Léon
(2021/06/07)
Gas phase surface-catalyzed HCl addition to vinylacetylene: motion along a catalytic surface. Experiment and theory
Gaseous mixtures of HCl and vinylacetylene were permitted to react in Pyrex IR cells (NaCl windows). Gaseous 4-chloro-1,2-butadiene and 2-chloro-1,3-butadiene (chloroprene) were the major products. Kinetic data (FTIR) generated a rate expression in concert with surface catalysis. Computational studies involving surface associated water provide a view that accounts for the experimentally determined orders and a bifurcated pathway producing both products. The results are in accord with wall-adsorbed reactant(s) as well as previously reported computational studies on the reactants.
Mascavage, Linda M.,Zhang-Plasket, Fan,Sonnet, Philip E.,Dalton, David R.