Ligand-redox assisted nickel catalysis toward stereoselective synthesis of (n+1)-membered cycloalkanes from 1,n-diols with methyl ketones

• Published in: Chemical science (Cambridge) Vol. 12; no. 42; pp. 14217 - 14223
• Main Authors: Bains, Amreen K., Kundu, Abhishek, Maiti, Debabrata, Adhikari, Debashis
• Format: Journal Article
• Language: English
• Published: CAMBRIDGE Royal Soc Chemistry 03.11.2021; Royal Society of Chemistry; The Royal Society of Chemistry
• Subjects: Alkylation; Cascade chemical reactions; Catalysis; Catalysts; Chemical synthesis; Chemistry; Chemistry, Multidisciplinary; Cycloalkanes; Dehydrogenation; Diols; Hydrogenation; Interception; Ketones; Ligands; Metal hydrides; Nickel; Physical Sciences; Science & Technology; Stereoselectivity; SECONDARY ALCOHOLS; FUNCTIONALIZATION; DEHYDROGENATION; BORROWING HYDROGEN; CONSTRUCTION; N-ALKYLATION; IRON; STEP; INDOLES
• ISSN: 2041-6520; 2041-6539
• DOI: 10.1039/d1sc04261k

A well-defined, bench-stable nickel catalyst is presented here, that can facilitate double alkylation of a methyl ketone to realize a wide variety of cycloalkanes. The performance of the catalyst depends on the ligand redox process comprising an azo-hydrazo couple. The source of the bis electrophile in this double alkylation is a 1,n-diol, so that (n+1)-membered cycloalkanes can be furnished in a stereoselective manner. The reaction follows a cascade of dehydrogenation/hydrogenation reactions and adopts a borrowing hydrogen (BH) method. A thorough mechanistic analysis including the interception of key radical intermediates and DFT calculations supports the ligand radical-mediated dehydrogenation and hydrogenation reactions, which is quite rare in BH chemistry. In particular, this radical-promoted hydrogenation is distinctly different from conventional hydrogenations involving a metal hydride and complementary to the ubiquitous two-electron driven dehydrogenation/hydrogenation reactions.