MANGANESE(III)-BASED OXIDATIVE FREE-RADICAL CYCLIZATION OF UNSATURATED BETA-KETO-ESTERS, 1,3-DIKETONES, AND MALONATE DIESTERS
MANGANESE(III)-BASED OXIDATIVE FREE-RADICAL CYCLIZATION OF UNSATURATED BETA-KETO-ESTERS, 1,3-DIKETONES, AND MALONATE DIESTERS
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DOI：
10.1021/jo00295a035
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发表时间：
1990-04-13
影响因子：
3.6
通讯作者：
SNIDER, BB
中科院分区：
文献类型：
--
作者：
KATES, SA;DOMBROSKI, MA;SNIDER, BB
描述了用2当量的Mn（0Ac）3·2 H20和1当量的Cu（0Ac）2·H20对不饱和正-酮基酯、1，3-二酮和丙二酸二酯进行氧化自由基环化。d-酮酯1用Mn（III）氧化成烯醇自由基2，然后6-外环化得到自由基4，其被Cu（II）氧化得到烯烃7，产率为64-71%。9的氧化得到较低产率的5-外型环化产物11，这是由于竞争性过氧化得到13。18的氧化环化得到叔自由基19，其进一步氧化成阳离子20。n-取代的α-酮基酯23、33和37的氧化以高产率进行，因为产物不能被进一步氧化。不饱和环状双酮酯40 a和45的氧化环化有效地进行，得到双环加合物42、44和47。4-烯基-2-甲基环戊烷-1，3-二酮54、61和64的氧化环化提供双环[3.2. 1]辛二酮57、63和双环[3.3. 1]壬二酮66和67的产率中等。这些研究表明，锰（III）为基础的氧化自由基环化是一个强大的合成方法，描绘了这个反应的范围和局限性，并建议进一步探索的途径。
Oxidative free-radical cyclizations of unsaturated ß-keto esters, 1, 3-diketones, and malonate diesters with 2 equiv of Mn (0Ac) 3-2H20 and 1 equiv of Cu (0Ac) 2-H20 are described. Oxidation of d-keto ester 1 with Mn (III) to enol radical 2 followed by 6-exo cyclization gives radical 4, which is oxidized by Cu (II) to give alkene 7 in 64-71% yield. Oxidation of 9 gives a lower yield of 5-exo cyclization product 11 due to competingoveroxidation to give 13. Oxidative cyclization of 18 gives the tertiary radical 19, which is further oxidized to cation 20. Oxidation of «-substituted ß-keto esters 23, 33, and 37 proceeds in high yield since the product cannot be oxidized further. Oxidative cyclization of unsaturated cyclic ß-keto esters 40a and 45 proceeds efficiently to give bicyclic adducts 42, 44, and 47. Oxidative cyclizations of 4-alkenyl-2-methylcyclopentane-l, 3-diones 54, 61, and 64 provide bicyclo [3.2. 1] octanediones 57, 63, and bicyclo [3.3. 1] nonanediones 66 and 67 in moderate yields. These studies indicate that Mn (III)-based oxidative free-radical cyclization is a powerful synthetic method, delineate the scope and limitations of this reaction, and suggest further avenues for exploration.