Hayashi Hiroyuki, Yasukochi Shotaro, Sakamoto Tatsuhiro, Hatano Manabu, Ishihara Kazuaki
Graduate School of Engineering, Nagoya University, Nagoya 464-8603, Japan.
Graduate School of Pharmaceutical Sciences, Kobe Pharmaceutical University, Kobe 658-8558, Japan.
J Org Chem. 2021 Apr 2;86(7):5197-5212. doi: 10.1021/acs.joc.1c00102. Epub 2021 Mar 15.
Insight into the mechanism of a safe, simple, and inexpensive phosphoric acid (HPO)-catalyzed acylation of alcohols with acid anhydrides is described. The corresponding in situ-generated diacylated mixed anhydrides, unlike traditionally proposed monoacylated mixed anhydrides, are proposed as the active species. In particular, the diacylated mixed anhydrides act as efficient catalytic acyl transfer reagents rather than as Brønsted acid catalysts simply activating acid anhydrides. Remarkably, highly efficient phosphoric acid (1-3 mol %)-catalyzed acylation of alcohols with acid anhydrides was achieved and a 23 g scale synthesis of an ester was demonstrated. Also, phosphoric acid catalyst was effective for synthetically useful esterification from carboxylic acids, alcohols, and acid anhydride. Moreover, with regard to recent developments in chiral 1,1'-bi-2-naphthol (BINOL)-derived phosphoric acid diester catalysts toward asymmetric kinetic resolution of alcohols by acylation, some phosphate diesters were examined. As a result, a P NMR study and a kinetics study strongly supported not only the acid-base cooperative mechanism as previously proposed by other researchers but also the mixed anhydride mechanism as presently proposed by us.
本文描述了对一种安全、简单且廉价的磷酸（HPO）催化醇与酸酐酰化反应机理的深入研究。与传统提出的单酰化混合酸酐不同，相应的原位生成的二酰化混合酸酐被认为是活性物种。特别地，二酰化混合酸酐作为高效的催化酰基转移试剂，而不仅仅是作为简单活化酸酐的布朗斯特酸催化剂。值得注意的是，实现了高效的磷酸（1 - 3 mol%）催化醇与酸酐的酰化反应，并展示了23 g规模的酯合成。此外，磷酸催化剂对于由羧酸、醇和酸酐进行的具有合成价值的酯化反应也有效。而且，关于手性1,1'-联二萘酚（BINOL）衍生的磷酸二酯催化剂在通过酰化对醇进行不对称动力学拆分方面的最新进展，研究了一些磷酸二酯。结果，一项³¹P NMR研究和一项动力学研究不仅有力地支持了其他研究人员先前提出的酸碱协同机理，也支持了我们目前提出的混合酸酐机理。
