A highly diastereoconvergent Friedel–Crafts alkylation reaction of 2-naphthol derivatives with diastereomixtures of diarymethanols bearing a designed chiral auxiliary was achieved by using tin(IV) bromide as a catalyst in nitromethane under mild reaction conditions. The effects of various substituents located on the chiral auxiliary were evaluated, and chiral induction was found to take place via a carbocation through the chelation effect of an oxygen atom in a stereoconvergent manner. The chiral auxiliary was easily deprotected under conventional hydrogenation conditions without affecting the chirality of the starting material. A variety of substrates were transformed successfully, with high yields and selectivities (diastereomeric ratios ≥ 20:1) obtained irrespective of the substitution pattern and the electronic nature of the substrate aromatic rings.

An efficient acylative kinetic resolution of racemic aromatic β-hydroxy esters with cyclohexanecarboxylic anhydride was achieved using newly designed (R)-N-methylbenzoguanidine ((R)-NMBG) derivatives. A series of (R)-NMBG derivatives was synthesized by modifying the original (R)-NMBG catalyst with the introduction of branched N-substituents containing a stereogenic center, and their catalytic performance was evaluated. (R,R)-N-(1-(β-1-Naphthyl)ethyl)benzoguanidine [(R,R)-NβNpEtBG] was found to function as an efficient acyl transfer catalyst for the reaction of a broad variety of substrates, regardless of the substituent type and substitution pattern.Download high-res image (91KB)Download full-size image

•The kinetic resolution of racemic β-hydroxy esters was achieved.•(R)-NMBG functioned as an efficient acyl transfer catalyst.•The effect of the structure of the ester moiety was investigated.•Cyclohexane carboxylic anhydride was a suitable acyl donor.(R)-(+)-N-methylbenzoguanidine ((R)-NMBG) functioned as an efficient acyl transfer catalyst for the acylative kinetic resolution of racemic β-hydroxy esters using cyclohexane carboxylic anhydride under mild reaction conditions. A tert-butyl ester moiety is necessary to achieve a high selectivity. The effects of the substituents on the aromatic rings of the substrates were systematically investigated, and diverse substrates participated in the reaction with good s-values (>20) irrespective of the type of substituents and their patterns, except for o-methoxy group.

•SnBr4-promoted Friedel–Crafts alkylation reaction was developed.•A variety of substrates were applied.•The reaction intermediates were examined.•A catalytic reaction pathway was proposed.Tin(IV) bromide was found to act as an efficient Lewis acid catalyst for the Friedel–Crafts type dehydrative alkylation reaction of diarylmethanols with 2-naphthol derivatives under mild conditions. The effects of the substituents on the substrates were systematically evaluated, and the reaction could be applied to a variety of substrates by tuning the conditions depending on the electronic properties of the starting materials.

Intramolecular decarboxylative etherification of readily available benzylic carbonates derived from benzylic alcohols and chloroformates was achieved using InCl3 in an SN1-type reaction. A fairly broad range of substrates could be used for the reaction by tuning the conditions depending on the electron density of the substituents on the substrates. A variety of secondary benzyl–alkyl, –allyl, –benzyl, and –aryl ethers were readily produced using the novel protocol under mild reaction conditions.