Premium
Selective Activation of Aromatic Aldehydes Promoted by Dispersion Interactions: Steric and Electronic Factors of a π‐Pocket within Cage‐Shaped Borates for Molecular Recognition
Author(s) -
Tanaka Daiki,
Tsutsui Yuya,
Konishi Akihito,
Nakaoka Koichi,
Nakajima Hideto,
Baba Akio,
Chiba Kouji,
Yasuda Makoto
Publication year - 2020
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.202003594
Subject(s) - chemistry , chemoselectivity , lewis acids and bases , electrophile , steric effects , electrophilic aromatic substitution , intramolecular force , catalysis , molecular recognition , aromaticity , lewis acid catalysis , electronic effect , selectivity , combinatorial chemistry , organic chemistry , molecule
Selective bond formations are one of the most important reactions in organic synthesis. In the Lewis acid mediated electrophile reactions of carbonyls, the selective formation of a carbonyl–acid complex plays a critical role in determining selectivity, which is based on the difference in the coordinative interaction between the carbonyl and Lewis acid center. Although this strategy has attained progress in selective bond formations, the discrimination between similarly sized aromatic and aliphatic carbonyls that have no functional anchors to strongly interact with the metal center still remains a challenging issue. Herein, this work focuses on molecular recognition driven by dispersion interactions within some aromatic moieties. A Lewis acid catalyst with a π‐space cavity, which is referred to as a π‐pocket , as the recognition site for aromatic carbonyls is designed. Cage‐shaped borates 1 B with various π‐pockets demonstrated significant chemoselectivity for aromatic aldehydes 3 b – f over that of aliphatic 3 a in competitive hetero‐Diels–Alder reactions. The effectiveness of our catalysts was also evidenced by intramolecular recognition of the aromatic carbonyl within a dicarbonyl substrate. Mechanistic and theoretical studies demonstrated that the selective activation of aromatic substrates was driven by the preorganization step with a larger dispersion interaction, rather than the rate‐determining step of the C−C bond formation, and this was likely to contribute to the preferred activation of aromatic substrates over that of aliphatic ones.