Development of new carbon-carbon bond forming reactions through 1,4-migration of rhodium

• Main Author: Ming, Jialin
• Other Authors: Tamio Hayashi
• Format: Theses and Dissertations
• Language: English
• Published: 2018
• Subjects: DRNTU::Science::Chemistry::Organic chemistry::Organic synthesis; DRNTU::Science::Chemistry::Organic chemistry::Organometallic compounds
• Online Access: https://hdl.handle.net/10356/86053; http://hdl.handle.net/10220/46695
• Institution: Nanyang Technological University

This thesis documents our attempts to advance the chemistry of C–C bond forming reactions via 1,4-Rh shift. Chapter 1 is an introduction of rhodium-catalyzed C–C bond forming reactions and 1,4-migration of rhodium. In the first section of Chapter 1, catalytic reactions of rhodium with organometallics are discussed. This section has been further divided into three subsections: 1,4-additions to alkenes, 1,2-additions to carbonyl and imine compounds, and additions to alkynes. The second section is an introduction of 1,4-migration of rhodium and its applications to catalytic C–C bonds forming reactions. Chapter 2 describes our discovery of a reaction of potassium aryloxymethyltrifluoroborates with α,β-unsaturated carbonyl compounds in the presence of a chiral diene–rhodium catalyst, which introduces 2-methoxyaryl groups at the β-position of the α,β-unsaturated carbonyl compounds with high enantioselectivity in high yields. It may be surprising that these alkylboron reagents gave the hydroarylation products. The reaction is assumed to proceed through 1,4-Rh shift from aryloxymethyl–Rh intermediate to 2-methoxyaryl–Rh. The wide availability of phenol derivatives makes this asymmetric conjugate arylation synthetically useful. Chapter 3 describes the first example of catalytic arylstannylation of alkynes. The reaction of arylstannanes ArSnR3 with unfunctionalized alkynes was found to proceed in the presence of a rhodium catalyst and a catalytic amount of zinc chloride to give ortho-alkenylarylstannanes with high selectivity in high yields. The catalytic cycle is very unique, consisting of three transmetalation steps, from Sn to Rh, Rh to Zn, and Zn to Sn, in addition to arylrhodation of the alkyne followed by 1,4-migration of Rh from the 2-arylalkenyl carbon to the ortho-alkenylaryl carbon. Chapter 4 describes the first example of carbozincation of unfunctionalized alkynes using Rh catalysis. The addition of arylzinc reagents ArZnCl to alkynes was found to be catalyzed by rhodium complexes in the presence of a catalytic amount of zinc chloride. The selectivity in giving 2-arylalkenylzinc species or ortho-alkenylarylzinc species, the latter of which is generated through 1,4-Rh migration from alkenyl to aryl in the catalytic cycle, is controlled by the ligand on rhodium. Ligands cod and binap gave 2-arylalkenylzinc species and ortho-alkenylarylzinc species, respectively, with high selectivity.