Tetrabutylammonium dichlorobromate

Moreover, Negoro et al. reported that the reaction of alkenes and their related compounds with tetrabutylammonium dichlorobromate (TBA BrCl2) in chloroform gave bromochloro-adducts through stereospecific anti-addition (Fig. 19) (ref. 30). 

A completely different stereoselectivity, with respect to BrCl, has more recently been observed with tetrabutylammonium dichlorobromate as a bromochlorinating agent78. The reaction of this electrophile with 1,3-butadiene, isoprene, cis- and fraws-l,3-pentadienes and cyclopentadiene gives selectively, in good yields, the corresponding 1,2-bromochloro adducts. Moreover, the addition to the 3,4-bond of pentadienes and to cyclopentadiene proceeds with a complete anti stereoselectivity. In the case of the unsubstituted butadiene the reaction gives a mixture of Markovnikov and anti-Markovnikov 1,2-adducts (equation 46). 

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