Year: 2023
Type: editorial
Abstract: Carboxylic acids are common intermediates within pharmaceutical synthesis, and alternative methods for their reduction to the corresponding alcohols are of interest.A recent report from Ramachandran and co-workers (Org.Lett., DOI: 10.1021/acs.orglett.2c03326)describes the use of ammonia borane (NH 3 -BH 3 ) in combination with catalytic TiCl 4 to reduce a range of alkyl and aryl carboxylic acids.This builds upon longstanding uses of amine boranes for carbonyl reductions, along with the Ramachandran group's earlier use of ammonia borane for hydroboration of ketones.Employing 2 equiv of ammonia borane in combination with 10 mol % TiCl 4 at room temperature, a wide range of carboxylic acids could be reduced in typically good yield (>40 examples, typically >70% yield).The reaction was also demonstrated at a 100 mmol scale in 95% yield, although this required an increased loading of 15 mol % TiCl 4 .The chemoselectivity of the reduction was investigated, showing good selectivity for carboxylic acid reduction versus amide and nitrile functionality and moderate selectivity versus esters.Ketones were reduced in preference to the carboxylic acids.One current limitation to implementation on scale is the current requirement for Et 2 O as the solvent, with THF resulting in significantly reduced yield. ■ PHOTOCATALYTIC ALKYLATION OF C(sp 3 )-H BONDS USING SULFONYLHYDRAZONESThe tactical introduction of C(sp 3 )-C(sp 3 ) bonds at specific sites remains one of the most arduous tasks for synthetic chemists.Unlike disconnections between C(sp 3 )-Y or C-(sp 2 )-C(sp 3 ) bonds, traditional approaches are complicated by varying degrees of nucleophilicity, inefficiency in crosscoupling, and heightend basicity of carbanions.Simply put, for
Language: English
Subfield: Organic Chemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: bronze
OpenAlex ID: W4319337181