英语翻译Recent developments in radical reactions involving phosp

英语翻译
Recent developments in radical reactions involving phosphorus
reagents have attracted our attention.Hypophosphorous
acid and its corresponding 1-ethylpiperidine salt have
been used to mediate radical cyclization reactions as an
alternative to tributyltin hydride.[6,7] Diethyl phosphine oxide
(DEPO)[8] and diethyl phosphite[9,10] were also recently used
in radical processes.[11,12]
As diethyl phosphite is known to be a slower reducing
agent than tributyltin hydride and thiophenol,[13] we were
motivated to test the use of a phosphorus reagent in a radical
cascade involving the addition of a P radical onto a triple
bond followed by 1,5-hydrogen abstraction.To the best of our
knowledge,only one radical addition of a dialkyl phosphite to
a terminal triple bond has been reported,which was by Ishii
and co-workers using Mn(OAc)2 as a radical initiator in the
presence of air.[14] Parsons and co-workers reported the
failure of such a radical addition but presented one example
of a clean addition of a thiophosphite to a terminal alkyne.[15]
Herein,we report that dimethyl phosphite is a particularly
efficient reagent for radical additions to terminal alkynes
followed by 1,5-hydrogen transfer/cyclization processes.
Optimization of the reaction conditions were conducted
on substrate 1a [Eq.(3); DLP=dilauroyl peroxide].Highly
reproducible results and excellent yields were obtained by
treating a 0.1m solution of the alkyne 1a with five equivalents
of dimethyl phosphite and one equivalent of DLP[16] in
cyclohexane at reflux for 6 h.The desired cyclized product 2a
was obtained in 81% yield,and no trace of the product from
direct reduction was observed.In this particular example,
neither the procedure using tin hydride developed by Curran
and Shen[3] nor our procedure using thiophenol[4] [see Eq.(2)]
gave satisfactory results because of the slow rate of the
hydrogen-abstraction step.
Propargylmalonates 1b–e were then tested according to
Equation (4).The generation of a tertiary alkyl radical from
1b is very efficient with dimethyl phosphite (Table 1,entry 1),

最近涉及磷试剂基团反应方面的进展引起了我们的关注.次磷酸及其对应的N-乙基哌啶盐已经代替三丁基锡氢化物被用于基团环化反应的介质[6,7] .二乙基氧化膦(DEPO)[8]和亚磷酸二乙酯[9,10] 最近也被用于基团处理中[11,12] .由于亚磷酸二乙酯是一种比三丁基锡氢化物和[13]苯硫酚更温和的还原剂,促使我们来测试磷试剂在涉及磷基团物加成到三键上后继之以1,5-夺氢反应而产生的基团性级联反应中的应用.就我们所知,目前仅有一个把基团性亚磷酸二炔基酯加成到末端三键上的报道,是Ishii 及其同事们在空气存在的条件下用醋酸锰作为基团引发剂产生的反应 [14].Parsons及其同事们报道这样的基团性加成反应是失败的,但代表了亚磷酸酯清洁加成到 末端炔基上的一个事例[15].我们在本文报道,亚磷酸二甲酯是一种基团性加成到末端炔基然后进行1,5-氢转移/成环反应的一种尤其高效的试剂.
反应条件的优化在反应物1a 上进行[化学反应式 (3)；DLP代表二月桂酰基过氧化物].用5份当量（与下面的0.1ml对应的体积比）的亚磷酸二甲酯 和1份当量的二月桂酰基过氧化物[16]处理0.1m（可能掉了一个字母,应该是毫升）的炔烃溶液并在环己烷中回流6小时得到了高度可重复的结果和良好的产率.目标环化产物2a 产率为81%,且没有观察到痕量的直接消去反应产生的（副）产物.在这个特殊的反应事例中,这个反应步骤既没有使用 Curran和Shen[3]开发的锡氢化物也没有使用苯硫酚[4] [看化学反应式 (2)] 但却得到了满意的结果,这是由于夺氢反应步骤进行比较慢的原因.然后,根据化学反应式 (4)测试了炔丙醇的丙二酸酯1b–e .采用亚磷酸二甲酯从1b 生成叔烷基基团产物是非常高效的 (表1,第一组).