[Lewis Acid]+[Co(CO)4] Complexes: A Versatile Class of Catalysts for Carbonylative Ring Expansion of Epoxides and Aziridines

Abstract

Efficient carbonyl insertion into CO and CN bonds using [Lewis acid]+[Co(CO)4]− complexes 1 and 2 gives regio‐ and stereoselective carbonylation of a variety of epoxides and aziridines to yield β‐lactones and β‐lactams, respectively. Both transformations are proposed to occur by the same mechanism, yielding products with inversion of configuration at the site of CO insertion.

The effect of titanium alkoxides in the synthesis of heterobimetallic complexes by titanocene(III) alkoxide-induced metal–metal bond cleavage of metal carbonyl dimers

“…In typical examples, their catalysis has been investigated in hydroformylation [2][3][4][5], carbonylation [6], hydrogenation/isomerization [7], asymmetric synthesis [8][9][10][11], olefin methathesis [12], enol ester formation [13], and olefin polymerization [14]. In our previous papers, we have reported unique access to heterobimetallic complexes by reactions of titanocene t-butoxides, Cp 2 Ti(O t Bu) (Cp = g 5 -C 5 H 5 ; 1a) and Cp à 2 TiðO t BuÞ (Cp* = g 5 -C 5 Me 5 ; 2a), with certain metal carbonyl dimers, [CpM(CO) 3 ] 2 [M = Mo, W], [CpRu (CO) 2 ] 2 , and Co 2 (CO) 8 [15].…”

Rhodium-Catalyzed Carbonylative Skeleton Rearrangement of 1,4-Enynes Tethered by a Cyclopropane Group

“…Addition of NMO has been found to be able to accelerate the Pauson-Khand reaction by removing a CO ligand from the metal oxidatively as carbon dioxide, 18 but it was also ineffective to our reaction. Other additives such as AgSbF 6 and phosphine ligands 19 (C 6 F 5 ) 3 P, DPEphos and dppe have no effect to improve the yield of 2a ( be also noted that when this [Rh(CO) 2 Cl] 2 -catalyzed reaction was conducted without CO, the conversion of 1a was very low (<5%) and only trace amount of product 2a was afforded.…”

“…To a 25 mL flame-and vacuum-dried Schlenk tube were added the substrate 1 (0.2 mmol) and [Rh(CO) 2 Cl] 2 (0.005 mmol). The Schlenk tube was evacuated and backfilled with CO, then p-xylene (2 mL) was added, and the reaction mixture was allowed to stir at indicated temperature for 12 h. The product was purified by column chromatography or preparative silica gel plate using PE and EtOAc as eluent (PE-EtOAc = 8:1).…”

Synthesis of Saturated Heterocycles via Metal-Catalyzed Formal Cycloaddition Reactions That Generate a C–N or C–O Bond

“…Coates and co-workers later developed a more efficient catalyst, in which the cation of the zwitterionic cobalt catalyst is itself a Lewis acid (Scheme 7.18, B). [118][119] Best results were initially obtained with 18 an aluminium salen complex, but later other Lewis acids were found to be even more efficient. [120][121][122] Scheme 7.18: Formal [3+1] cycloaddition of epoxides and carbon monoxide.…”