Catalytic, asymmetric reactions of ketenes and ketene enolates

Inactivation of the particulate methane monooxygenase (pMMO) in Methylococcus capsulatus (Bath) by acetylene

“…The methyl ketene is expected to migrate more slowly away from the catalytic site where it is formed. This ketene derivative is also intrinsically less reactive compared with ketene [28,29]. Consistent with the results noted earlier for HCCH-treatment, simulation of the PmoC mass peak of the CH 3 CCH-treated pMMO after the 1-h reaction shows that ~50% of the PmoC subunits in the sample are chemically modified when the pMMO activity has become completely inhibited (Fig.…”

“…According to the predicted masses of the three subunits of pMMO [28,29], the 29 690 Da (or 30 kDa) subunit corresponds to the PmoC subunit. Earlier suicide substrate experiments using radioactive HCCH to label the subunits, followed by SDS-PAGE, and N-terminal amino acid sequencing [8] have implicated PmoA (earlier (vide infra) assignment of the "~27 kDa" protein band in the SDS-PAGE gel) as the subunit labeled.…”

Organocatalytic Asymmetric Cycloaddition Reaction of Ketenes

“…10 mol% 1c LiClO 4 , EtN(i-Pr) 2 Nelson 等认为该反应的机理是: 现场生成的烯酮在 亲核催化剂和 Lewis 酸作用下首先生成金属配位的烯醇 盐, 烯醇盐再通过一个含有金属离子的六元环状过渡态 与醛进行加成, 最后环化生成 β-内酯(Scheme 9). 六元 环状过渡态的形成, 不仅活化了底物, 而且创造了一个 紧密的手性控制环境, 使得 C-C 键的生成具有很高的 立体选择性.…”

Computational Study on the Intramolecular Carbene-CO Coupling in M(CH2)(CO)3 Radicals (M = Co, Rh, Ir)

“…Ketenes belong to the first generation of reactive intermediates [1], along with carbenes, radicals, carbocations, and carbanions [2], and are intensively studied members of the cumulene family, with a wide variety of synthetic applications [3][4][5][6]. The most common method to access ketenes is from acyl halides via dehalogenation promoted by bases.…”