Anri-Markovnikov addition

This alkyl halide can be made from the starting material by first moving the location of the % bond, followed by anri-Markovnikov addition ... 

The regioselective anri-Markovnikov addition of benzoic acid to phenylacetylene has also been carried out with success at 111°C in the presence of ruthenium complexes containing a tris(pyrazolyl)borate (Tp) ligand, [RuCl(Tp)(cod) (C),... 

The addition to allyl nitrile also shows some preference for the anri-Markovnikov adduct (equation III). However, both products undergo a Ritter-type hydrolysis of the nitrile group to provide the same lactone. 

In contrast to palladium and rhodium catalyzed monohydroboration of 1,3-dienes,20 no 1,4-addition and only 1,2-addition products were obtained with anri-Markovnikov regioselectivity. Acyclic dienes were more reactive than cyclic dienes, and styrene was unreactive. Among iron(II) and cobalt(II) chloride complexes with dppe, dppp and dppb only CoClz(dppp) showed catalytic activity albeit lower than NiCUIdppe). 

A variety of alkynes undergo regio- and stereoselective hydrothiolation with arenethiols in the presence of RhCl(PPh3)3. Ethanol and dichlorometane is suitable solvents for this hydrothiolation. This hydrothiolation proceeds well, even when galvinoxyl as a radical inhibitor is added to the reaction system. Recently, Wilkinson s catalyst is reported to be an excellent catalyst for alkyne hydrothiolation with alkanethiols to provide -isomers of anri-Markovnikov-type addition products 3 selectively [54]. 

Based on these observations, a possible catalytic cycle for the rhodium-catalyzed anfi-Markovnikov addition of thiols to alkynes is shown in Scheme 18. Oxidative addition of PhSH to WOkinson s catalyst generates hydrorhodium sulfide species (frans-HRhCl(SPh)(PPh3)2). After coordination of alkyne to the hydrorhodium sulfide species, stereoselective insertion of alkyne into Rh-H bond provides -isomer of vinylic rhodium intermediate. The subsequent reductive eliminatiOTi of anri-Markovnikov adduct in the presence of PhSH regenerates the hydrorhodium sulfide species. 

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