Annelated Pyridines as Highly Nucleophilic and Lewis Basic Catalysts for Acylation Reactions

Abstract

New heterocyclic derivatives of 9-azajulolidine have been synthesized and characterized with respect to their nucleophilicity and Lewis basicity. The Lewis basicity of these bases as quantified through their theoretically calculated methyl-cation affinities correlate well with the experimentally measured reaction rates for addition to benzhydryl cations. All newly synthesized pyridines show exceptional catalytic activities in benchmark acylation reactions, which correlate only poorly with Lewis basicity or nucleophilicity parameters. A combination of Lewis basicity with charge and geometric parameters in the framework of a three-component quantitative structure-activity relationship (QSAR) model is, however, highly predictive.

Boronic acid–DMAPO cooperative catalysis for dehydrative condensation between carboxylic acids and amines

“…Boronic acid 2 did not promote the reaction in the absence of additive under these conditions (entry 1). Tertiary amines such as N , N -diisopropylethylamine and 4-( N , N -dimethylamino)pyridine (DMAP) 11 were not effective as additives (entries 2 and 3). 4-Methoxypyridine N -oxide (MPO) was also less active (entry 4).…”

Pyridine–acetaldehyde, a molecular balance to explore the n→π*interaction

“…[20][21][22] Pyridine (PY) or its derivatives can be used as nucleophilic catalysts in acylation reactions. 23 The structures of pre-reactive intermediates of PY with carbonyl compounds are expected to show the signatures of the n* interactions as recently observed for the PY-formaldehyde (FA) adduct. 22 However, given the weakness of the n* interaction one wonders if this interaction would still prevail in PY complexes with aldehydes of increasing size, where steric interactions may bring the cluster geometry out of the Bürgi-Dunnitz trajectory (see Figure 1).…”

Chemoselectivity in Esterification Reactions – Size Matters after All

“…For activation, we decided to employ 9-azajulodine (TCAP) due to its well-documented high reactivity in acylation reactions. 5 Scheme 1 Competition experiment between secondary alcohols carrying alkyl and aryl substituents R 1 and R 2 of different effective surface Carboxylic acid derivatives carrying large aromatic or aliphatic substituents such as 1-adamantyl carboxylic acid 6 or the substituted benzoic anhydrides in the Yamaguchi 7 and Shiina 8 esterification reactions, respectively, are known to be capable of selective transformations. We therefore initiated our studies with reagents from this latter class and used acetyl chloride as the smallest possible reference.…”