Radical O→C Transposition: A Metal-Free Process for Conversion of Phenols into Benzoates and Benzamides
Radical O→C Transposition: A Metal-Free Process for Conversion of Phenols into Benzoates and Benzamides
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DOI：
10.1021/jo102467j
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发表时间：
2011-03-18
影响因子：
3.6
通讯作者：
Alabugin, Igor V.
中科院分区：
文献类型：
--
作者：
Baroudi, Abdulkader;Alicea, Jeremiah;Alabugin, Igor V.
我们报道了一种通过一种新的自由基级联反应将苯酚转化为苯甲酸酯和酰胺的无金属过程。二芳基硫代碳酸酯和硫代氨基甲酸酯可在单一高产率步骤中从苯酚中选择地在C=S部分的硫原子上加硅基。这一加成步骤类似于Barton-McCombie反应的第一步，通过O-新叶醇重排产生碳自由基经1，20-O-gt；C转位。可逆重排步骤中通常不利的平衡通过O中心自由基中高放热的C-S键断裂而前移，这提供了最终的苯甲酸酯或苯甲酰胺产品。由苯酚制备苯甲酸衍生物的无金属方法为金属催化的三氟代芳烃的羰基化反应提供了一种潜在的有用的替代方法。
We report a metal-free procedure for transformation of phenols into esters and amides of benzoic acids via a new radical cascade. Diaryl thiocarbonates and thiocarbamates available in a single high-yielding step from phenols, selectively add silyl radicals at the sulfur atom of the C=S moiety. This addition step, analogous to the first step of the Barton-McCombie reaction, produces a carbon radical which undergoes 1,2 O -> C transposition through an O-neophyl rearrangement. The usually unfavorable equilibrium in the reversible rearrangement step is shifted forward via a highly exothermic C-S bond scission in the O-centered radical, which furnishes the final benzoic ester or benzamide product. The metal-free preparation of benzoic acid derivatives from phenols provides a potentially useful alternative to metal-catalyzed carbonylation of aryl triflates.