Tellurium-Mediated Halogen Transer from Polyhaloalkanes to Diyne Acceptors

Article abstract of DOI:10.1021/jo00120a015

Elemental tellurium catalyzes transfer of halogen from (CHCl2)2, from C2HCl5 and from (CHBr2)2, to the phenylated diynes 1-3, 17, 20, and 24, in which the alkyne moieties are in close proximity.The process is associated with cyclorearrangement reactions by which halogenated polycycles are formed.In boiling C2HCl5, derivatives of 1,2-bis(phenylethynyl)benzenes afford 5-halogenated indeno<2,1-a>indenes, 1,8-bis(phenylethynyl)naphthalene gives a chlorinated benzofluoranthene derivative, and 2,2'-bis(phenylethynyl)<1,1'-biphenyl> forms 9-chloro-14-phenylbenzanthracene.Diynes 25 and 26 in which the ethynyl functions are further removed from each other fail to yield halogenated products.Diyne 25 undergoes oxidative cyclization by which 1,3-diphenyldibenzo<3,4:6,7>cyclohepta<1,2-c>furan (29) is formed.Compound 26 is transformed to hydrocarbon 32, which involves a phenyl ring walk and elimination of H2Te.