Regioselective Carbonylation of 2,2-Disubstituted Epoxides: An Alternative Route to Ketone-Based Aldol Products

Abstract

We report the regioselective carbonylation of 2,2-disubstituted epoxides to β,β-disubstituted β-lactones. Mechanistic studies revealed epoxide ring-opening as the turnover limiting step, an insight that facilitated the development of improved reaction conditions using weakly donating, ethereal solvents. A wide range of epoxides can be carbonylated to β-lactones, which are subsequently ringopened to produce ketone-based aldol adducts, providing an alternative to the Mukaiyama aldol reaction. Enantiopure epoxides were demonstrated to undergo the carbonylation/ringopening process with retention of stereochemistry to form enantiopure β-hydroxy esters.

Cobalt Carbonyls Stabilized by N,P‐Ligands: Synthesis, Structure, and Catalytic Property for Ethylene Oxide Hydroalkoxycarbonylation

“…To this regard, we performed density functional theory (DFT) study. The theoretical investigations on the homogeneous catalytic transformation of EO and CO into β‐lactone, which includes elemental reaction steps as EO ring opening, CO insertion, and β‐lactone formation, have indicated that the initial EO ring opening was presumably conducted under a cooperative interaction mode by combination of the [Co(CO) 4 ] − and Lewis acid, [7a,k–m] as the naked [Co(CO) 4 ] − seemed hard to complete this reaction [10] . In comparison, the catalytic reaction of EO, CO, and MeOH into 3‐HMP may involve the 3‐HMP formation reaction as the terminal step besides the EO ring opening and CO insertion.…”

“…Of significance is the unambiguous authentication of the X‐ray molecular structure of these ion‐pair complexes, as provides a direct view of their catalytic functions. So far, the [Lewis acid] + part has been disclosed for the aluminum [7b,i–l] or chromium [7c,d,g,l,m] cations ligated by salen‐type or porphyrin ligands, together with one example of a titanocene cation [7a] . These ion‐pairs are generally prepared from a metathesis reaction using NaCo(CO) 4 with the related ligand‐coordinated metal halides.…”

Formation of mononuclear N,O-chelate zirconium complexes by direct insertion of epoxide into tetrakis(dimethylamido)zirconium: highly promising approach for developing an ALD precursor of ZrO2 thin films

“…MCO was synthesized according to a previously reported procedure. 22 Typically, m CPBA (22.76 g) was added slowly to a solution of methylenecyclohexane (8.30 g) in CH 2 Cl 2 (300 mL) at 0 °C at a stirring rate of 600 rpm. The reaction mixture was warmed to room temperature and stirred for 24 h. To decompose the residue of m CPBA, aqueous Na 2 S 2 O 3 (4.10 g, 30 mL H 2 O) was added to the mixture, which was stirred for an additional 2 h. After filtering the solution through Celite, the aqueous phase was extracted twice with CH 2 CH 2 .…”

“…MCO was synthesized according to a previously reported procedure. 22 Typically, mCPBA (22.76 g) was added slowly to a Scheme 1 Synthesis of N,O-chelate Zr compound via the conventional method and developed method.…”

Catalytic Reactions by Heterobimetallic Carbonyl Complexes with Polar Metal–Metal Interactions

“…In 2019, the Coates lab developed a series of new [(porphyrin)Al(THF) 2 ] + [Co(CO) 4 ]catalysts that enabled the highly efficient and regioselective carbonylation of 2,2-disubstituted epoxides to afford various ,-disubstituted -lactones under mild conditions (Scheme 14). 34 Compared with the first generation carbonylation catalyst [(porphyrin)Al(THF) 2 ] + [Co(CO) 4 ] -, the catalysts N and O showed higher turnover frequencies with versatile 2,2-disubstituted epoxides. Octaethylporphyrin catalyst N displayed high regioselectivity and good activity in the carbonylation of alkyl 2,2-disubstituted epoxides; while other epoxide substrates equipped with aromatic groups, TBS-protected alcohols, or methacrylate-derived substituents were carbonylated by the more economic and accessible catalyst O at higher temperatures.…”