Hydrochlorination alkenes

Hydrochlorination. The addition of hydrogen chloride to alkenes in the absence of peroxides takes place by an electrophilic substitution mechanism. The orientation is in accord -with Markovnikov s mle in -which the hydrogen atom adds to the side of the double bond that -will result in the... 

Another convenient procedure for hydrochlorination involves adding trimethylsilyl chloride to a mixture of an alkene and water. Good yields of HC1 addition products (Markovnikov orientation) are formed.3 4 These conditions presumably involve generation of HC1 by hydrolysis of the silyl chloride, but it is uncertain if the silicon plays any further role in the reaction. 

The MesSiCl and water system is a convenient reagent for the selective hydrochlorination of alkenes. The anti selective manner of addition was shown to occur by reacting 9(10)-octalin to afford 4a-chloro-frans-decahydronaphthaline exclusively.566... 

Occasionally aqueous solutions of HC1 have been employed in the hydrochlorination of alkenes (equations 42 and 43).67,68 The latter procedure appears quite general and avoids the difficulties of working with gaseous HC1. 

Hydrogen chloride, generated by mixing AcCl with EtOH, brings about Markovnikov hydrochlorination of alkenes in excellent yields. The products can be isolated in high purity by removal of the volatile components under reduced pressure.45... 

Tosyl chloride 361 can be applied similarly (entry 23) [404], Here the best cobalt complex was dependent on the structure of the starting olefin. For terminal alkenes 2 mol% of the (salen)Co complex 357a was preferred. Secondary alkyl chlorides were obtained with complete regioselectivity in 73-94% yield, while the catalyst derived from Co(BF4)2 and /V-salicylidene diphenylglycinate 353 proved to be better for the hydrochlorination of 1,1-disubstituted olefins (entry 22). Tertiary alkyl chlorides 362 were obtained in 67-96% yield. The reaction conditions are mild so that acid- and base-sensitive protecting groups are compatible. 

The formation of isopropyldichlorosilane can be explained by the reaction of elemental silicon with, hydrogen chloride and isopropyl chloride formed by the hydrochlorination of propylene. As an alternative, it is possible that a silicon-carbon bond is formed by the reaction of a silylene intermediate, generated on the surface of silicon metal powders, with alkene... 

Trimethylsilyl chloride is a convenient source of HCl for hydrochlorination of alkenes (15 examples, 65-99%). The generation of HCl in situ is accomplished by the decomposition of MCjSiCl with water. 

The intervention of carbocations in the electrophilic additions of hydrogen halides to alkenes has important stereochemical consequences. Consider, for example, the hydrochlorination of cis- and trans-2-hulene. Both give the same product, 2-chlorobutane, as a racemic mixture. We can nnderstand this ontcome by formulating the mechanism. 

Fabio Doctorovich of the Universidad de Buenos Aires reported (/. Org. Chem. 2008, 73, 5379) that hydroxylamme in the presence of an Fe catalyst reduced alkenes such as 1, but not ketones or esters. Erick Carreira of ETH Zurich developed (Angew. Chem. Int. Ed. 2008, 47, 5758) mild conditions for the hydrochlorination of mono-, di- and trisubstituted alkenes. Ramgopal Bhattacharyya of ladavpur University established Tetrahedron Lett. 2008, 49, 6205) a simple Mo-catalyzed protocol for alkene epoxidation. 

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