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Development of a Simple Adjustable Zinc Acid/Base Hybrid Catalyst for C−C and C−O Bond‐Forming and C−C Bond‐Cleavage Reactions
Author(s) -
Yamashita Yasuhiro,
Minami Kodai,
Saito Yuki,
Kobayashi Shū
Publication year - 2016
Publication title -
chemistry – an asian journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 106
eISSN - 1861-471X
pISSN - 1861-4728
DOI - 10.1002/asia.201600682
Subject(s) - catalysis , bond cleavage , zinc , cleavage (geology) , chemistry , bond , simple (philosophy) , base (topology) , polymer chemistry , stereochemistry , organic chemistry , materials science , mathematics , composite material , business , mathematical analysis , philosophy , finance , epistemology , fracture (geology)
A newly designed zinc Lewis acid/base hybrid catalyst was developed. By adjusting the Lewis acidity of the zinc center, aldol‐type additions of 2‐picolylamine Schiff base to aldehydes proceeded smoothly to afford syn ‐aldol adduct equivalents, trans ‐ N , O ‐acetal adducts, in high yields with high selectivities. NMR experiments, including microchanneled cell for synthesis monitoring (MICCS) NMR analysis, revealed that anti ‐aldol adducts were formed at the initial stage of the reactions under kinetic control, but the final products were the trans ‐( syn )‐ N , O ‐acetal adducts that were produced through a retro‐aldol process under thermodynamic control. In the whole reaction process, the zinc catalyst played three important roles: i) promotion of the aldol process (C−C bond formation), ii) cyclization process to the N , O ‐acetal product (C−O bond formation), and iii) retro‐aldol process from the anti ‐aldol adduct to the syn ‐aldol adduct (C−C bond cleavage and C−C bond formation).