Journal of the Chemical Society. Perkin transactions II p. 1195 - 1200 (1988)
Update date:2022-08-11
Topics:
Baban, Jehan A.
Roberts, Brian P.
Methyl bromoacetate and ethyl 2-bromopropanoate are reduced by Bun3P->BH3 or Bun3P->BH2Ph to methyl acetate and ethyl propanoate, respectively, in chlorobenzene at 80-110 deg C in the presence of dibenzoyl peroxide or t-butyl perbenzoate.Amine complexes of borane or phenylborane are much less effective reducing agents.The reductions may also be initiated photochemically and are inhibited by a phenolic radical scavenger.A homolytic chain mechanism is proposed in which the phosphine-boryl radical abstracts halogen from the bromo ester and is subsequently regenerated by reaction of an α-(alkoxycarbonyl)alkyl radical with the phosphine-borane.The latter propagation step, together with halogen abstraction from RI and addition of the derived alkyl radical to the C=C bond, is also involved in the chain reaction between Bun3P->BH2Ph, an alkyl iodide, and ethyl acrylate according to equation (A); Bun3P->BH3 reacts similarly but gives lower yields of ester.Reaction (A) proceeds smoothly at 110 deg C Bun3P->BH2Ph + RI + CH2=CHCO2Et -> RCH2CH2CO2Et + Bun3P->BHIPh (A) when initiated by t-butyl perbenzoate and moderate yields of isolated esters were obtained from n-butyl iodide, cyclohexyl iodide, and 3β-iodocholest-5-ene.This last iodide gives an epimeric mixture of 3α- and 3β-esters in total isolated yield of ca. 50 percent.Similar addition reactions take place between Bun3P->BH2Ph, BunI, and diethyl vinylphosphonate or phenyl vinyl sulphone.It is concluded that Bun3P->BH3 and particularly Bun3P->BH2Ph offer promise as alternatives to tin, mercury, and germanium hydrides in radical chain reactions of synthetic value.
View MoreShanghai Yuanding Chem. Sci. & Tech. Co., Ltd.
website:http://www.shydtec.com
Contact:86-21-57721279
Address:Science and Technology Park, Songjiang District, Shanghai, China
Xiamen Kaijia Imp & Exp Co., Ltd.
Contact:86-592-5101177
Address:Room406 Luhui Building No. 65 Haitian Road Huli Xiamen,China.
website:http://www.sjc.com.tw
Contact:(886) 2-2396-6223
Address:14Fl., No. 99. Sec. 2, Jen Ai Road
Dalian RSD International Trade Co.,Ltd.(expird)
Contact:86-22-60875058 58610575
Address:Wantong International Areas, Hongqiao District, Tianjin, China.China
shanghai tuomiao chemicial co.,ltd.
website:https://www.tuomiaochem.com/
Contact:021 - 59853336
Address:shanghai
Doi:10.1021/acs.cgd.5b00039
(2015)Doi:10.1021/acs.orglett.1c01270
(2021)Doi:10.1002/pola.24494
(2011)Doi:10.1021/acs.orglett.6b03229
(2016)Doi:10.1039/a900028c
(1999)Doi:10.1002/adsc.201700535
(2017)
