The Pd - tppts - HOTs (tppts = P(C6H4-m-SO3Na)3, HOTs = p-toluenesulfonic acid) catalyzed hydrocarboxylation of N-allylacetamide in an aqueous medium afforded 4-acetamidobutyric acid and 3-acetamido-2-methylpropanoic acid under mild conditions, with a high regioselectivity towards the linear isomer. During the hydrocarboxylation an acid catalyzed hydrolysis of the amide moieties of both the substrate and the products took place, as well as the formation of acetamide and propanal, presumably via a Pd-catalyzed allylic substitution reaction of N-allylacetamide. The hydrolysis reaction was suppressed by lowering the amount of Brønsted acid cocatalyst (HOTs) or by employing a weaker Brønsted acid such as propanoic acid. The allylic substitution reaction was minimized by increasing the CO pressure but unfortunately this caused a decrease in the regioselectivity. A sudden inhibition took place after ca. 70% conversion, presumably caused by one of the side products. By increasing the tppts concentration to 13.1 mmol L-1 (20 equiv per Pd) the inhibition was circumvented and a quantitative conversion of N-allylacetamide was achieved.Key words: aqueous media, olefins, palladium, hydrocarboxylation, N-allylacetamide.
Pd-tppts-HOTs(tppts = P(C6H4-m-SO3Na)3,HOTs =对甲苯磺酸)催化的N-烯丙基乙酰胺的水相加氢羧化反应,在温和条件下得到4-乙酰胺基丁酸和3-乙酰胺基-2-甲基丙酸,具有高选择性向线性异构体。在加氢羧化反应中,底物和产物的酰胺基团发生了酸催化的水解反应,同时通过Pd催化的烯丙基取代反应形成了乙酰胺和丙醛。通过降低Brønsted酸助催化剂(HOTs)的用量或使用较弱的Brønsted酸(如丙酸)可以抑制水解反应。通过增加CO压力可以最小化烯丙基取代反应,但不幸的是,这会导致选择性下降。反应约转化70%后发生了突然的抑制,可能是由于其中一个副产物引起的。通过将tppts浓度增加到13.1毫摩尔L-1(每个Pd 20当量)可以避免抑制,并实现对N-烯丙基乙酰胺的定量转化。关键词:水相媒介、烯烃、钯、加氢羧化、N-烯丙基乙酰胺。