Tetrakis borate copper complexes

BN RhC44HM, Rhodium , tetrakis(l-isocy-anobutane)-, tetraphenylborate(l -), 21 50 BN C Hio, Borate(l -), hydrotris(pyrazolato)-, copper complex, 21 108 BN6Ci5H22, Borate(l -), tris(3,5-dimethylpyr-azolato)hydro-, copper complex, 21 109 BN8Ci2Hi2, Borate(l-), tetrakis(pyrazolato)-, copper complex, 21 110 BjFeN CjoH,, Iron(II), [tris[p.-[(l,2-cy-clohexanedione dioximato)-0 0 ]diphenyl-diborato(2 — )]-NJI JI" X " JI"",... 

Similarly, the nitrene transfer reaction from 128 is facilitated by a variety of catalysts, including MTO (136) <01JCS(CC)235>, the lri(pyrazolyl)borate-coppcr(l) complex 137 <01OL1423>, and tetrakis(acetonitrile)copper(I) hexafluorophosphate (138) <01JA7707>. In the latter case, the reaction can be carried out using a sulfonamide and the primary oxidant, iodosylbenzene, whereby the actual nitrene transfer reagent 128 is presumed to be formed in situ. In all cases, acetonitrile appears to be the solvent of choice. 

A complementary, but less pronounced, increase in cis syri) selectivity is provided when diazoacetates with rather small ester groups and rhodium catalysts with bulky ligands, such as iodorhodium(IIl) porphyrins and mcso-tetrakis(2,4,6-triarylbenzoato)di-rhodium(ll) complexes, are employed. For ethyl 2-alkylcyclopropane-l-carboxylates so obtained, a cisfran.s ratio of 2-4 was typical. Notable cis selectivities have also been achieved in the synthesis of ethyl 2-phenylcyclopropane-l-carboxylate with the catalyst [(r/ -C5H5)Fe(CO)2(THF)][BFJ (cis/trans 5.25, see Section 1.2.1.2.4.2.6.3.1.) and copper catalysts prepared in situ from a copper salt [copper(I) iodide, copper(II) acetate or triflate] and sodium tetrakis(7,8,8-trimethyl-4,5,6,7-tetrahydro-2Ff-4,7-methanoindazolyl)borate (3) cis/ trans 2.1-3.2). °... 

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