SYNTHESIS OF HETEROCYCLES VIA PALLADIUM-CATALYZED CARBONYLATION OF ORTHO-SUBSTITUTED ORGANIC NITRO-COMPOUNDS IN RELATIVELY MILD CONDITIONS
SYNTHESIS OF HETEROCYCLES VIA PALLADIUM-CATALYZED CARBONYLATION OF ORTHO-SUBSTITUTED ORGANIC NITRO-COMPOUNDS IN RELATIVELY MILD CONDITIONS
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DOI：
10.1016/0304-5102(93)e0228-9
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发表时间：
1994-02-04
影响因子：
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通讯作者：
GIANELLA, E
中科院分区：
文献类型：
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作者：
TOLLARI, S;CENINI, S;GIANELLA, E
Pd(TMB)2/TMPhen/TMBH 催化体系 TMBH=2,4,6-三甲基苯甲酸催化醛存在下的邻硝基苯胺羰基化； TMPhen = 3,4,7,8-四甲基-1,10-菲咯啉）在140-180℃和20-40atm一氧化碳下，得到相应的苯并咪唑，选择性范围为10%至80%，很大程度上取决于所使用的醛。主要副产物是 2(1H) 苯并咪唑酮，由邻硝基苯胺直接羰基化衍生。相同的催化体系已用于邻硝基苯乙烯在120-180℃和20-60atm一氧化碳下的羰基化，获得相应的吲哚，选择性一般为70%至100%。有趣的是，在后一种情况下，为了获得良好的转化率和选择性，不需要 TMBH 的存在。相反，当硝基苯催化转化为异氰酸苯酯时，过量TMBH的存在是必不可少的。此外，在吲哚的催化合成中，没有形成羰基化产物。这些观察结果表明催化循环不同于在钯催化下由硝基苯合成异氰酸苯酯中所提出的催化循环。
Carbonylation of o-nitroaniline in the presence of aldehydes catalyzed by the Pd(TMB)2/TMPhen/TMBH catalaytic system TMBH=2,4,6-trimethyl benzoic acid; TMPhen = 3,4,7,8-tetramethyl-1,10-phenanthroline) at 140-180-degrees-C and 20-40 atm of carbon monoxide, gives the corresponding benzimidazoles, with a selectivity ranging from 10 to 80%, strongly depending on the aldehyde used. The main by-product was shown to be the 2(1H)benzimidazolone, derived by direct carbonylation of o-nitroaniline. The same catalytic system has been used in the carbonylation of o-nitrostyrenes at 120-180-degrees-C and 20-60 atm of carbon monoxide, obtaining the corresponding indoles with a selectivity generally ranging from 70 to 100%. Interestingly, in the latter case the presence of TMBH was not necessary in order to obtain good conversions and selectivities. On the contrary, the presence of excess TMBH is indispensable when nitrobenzene is catalytically converted to phenyl isocyanate. Moreover, in the catalytic synthesis of indoles no carbonylated products are formed. These observations suggest a catalytic cycle different from what has been proposed in the synthesis of phenyl isocyanate from nitrobenzene, catalyzed by palladium.