In:
Zeitschrift für Naturforschung B, Walter de Gruyter GmbH, Vol. 39, No. 5 ( 1984-5-1), p. 618-622
Abstract:
The reaction of CuCl 2 with equimolar quantities of an ylide R 3 P=CH 2 (1a-c, R=CH 3 , C 2 H 5 , C 6 H 5 ) in anhydrous tetrahydrofuran at low temperature leads to oxidative coupling, with ethylidene-1,2-bis-phosphonium salts R 3 P ⊕ -CH 2 -CH 2 -P ⊕ R 3 2X ⊖ (2, 3a-c) as high- yield products. The process is interpreted as a one-electron transfer to give radical cations R 3 P ⊕ -ĊH 2 (II) which subsequently undergo dimerization. The initial counterions CuCl 2 ⊖ (in 2a-c) can be replaced by PF 6 ⊖ (as in 3a-c). (C 2 H 5 ) 3 P=CHCH 3 (1d) yields the cation (C 2 H 5 ) 3 P ⊕ - * CH(CH 3 )- * CH(CH 3 )P ⊕ (C 2 H 5 ) 3 with two chiral centers as a mixture of diasteromers RR/SS, RS. The ratio of the components is 2,8:1. as evaluated by NMR spectroscopy. The analogous reaction with (C 6 H 5 ) 3 P=CHCH 3 and (C 6 H 5 ) 3 P=C(CH 3 ) 2 (1e, f) takes a very different course. Along with minor quantities of (C 6 H 5 ) 3 P ⊕ CH 2 CH 3 /(C 6 H 5 ) 3 P ⊕ CH(CH 3 ) 2 species, mainly 1-chloroalkyl-phosphonium cations are formed, which were again isolated as the hexafluorophosphates (4a, 4b: [(C 6 H 5 ) 3 P ⊕ CH(CI)CH 3 ]PF 6 ⊕ , [(C 6 H 5 ) 3 P ⊕ C(Cl)(CH 3 ) 2 ]Pf 6 ⊖ ). H-radical trapping from the medium by II ist proposed for the formation of the former, while a two- electron oxidation followed by addition of Cl ⊖ is the most plausible mechanism for the generation of the latter
Type of Medium:
Online Resource
ISSN:
1865-7117
,
0932-0776
DOI:
10.1515/znb-1984-0515
Language:
English
Publisher:
Walter de Gruyter GmbH
Publication Date:
1984
detail.hit.zdb_id:
2078109-X
detail.hit.zdb_id:
124635-5
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