38082-08-5Relevant academic research and scientific papers
Addition-Rearrangement of Ketenes with Lithium N- tert-Butanesulfinamides: Enantioselective Synthesis of α,α-Disubstituted α-Hydroxycarboxylic Acid Derivatives
Ma, Peng-Ju,Tang, Fan,Yao, Yun,Lu, Chong-Dao
supporting information, p. 4671 - 4675 (2019/06/17)
Addition of the lithium salts of chiral N-substituted tert-butanesulfinamides to ketenes and subsequent silylation initiates stereoselective [2,3]-rearrangement, which affords enantioenriched α,α-disubstituted α-sulfenyloxy carboxamides through a reaction
Stereo- and Chemodivergent NHC-Promoted Functionalisation of Arylalkylketenes with Chloral
Douglas, James J.,Churchill, Gwydion,Slawin, Alexandra M. Z.,Fox, David J.,Smith, Andrew D.
, p. 16354 - 16358 (2015/11/09)
Stereo- and chemodivergent enantioselective reaction pathways are observed upon treatment of alkylarylketenes and trichloroacetaldehyde (chloral) with N-heterocyclic carbenes, giving selectively either β-lactones (up to 88:12 dr, up to 94% ee) or α-chloroesters (up to 94% ee). Either 2-arylsubstitution or an α-branched iPr alkyl substituent within the ketene favours the chlorination pathway, allowing chloral to be used as an electrophilic chlorinating reagent in asymmetric catalysis.
Lewis acid-promoted ketene-alkene [2 + 2] cycloadditions
Rasik, Christopher M.,Brown, M. Kevin
, p. 1673 - 1676 (2013/04/10)
Described are the first examples of ketene-alkene [2 + 2] cycloadditions promoted by Lewis acids. Notable features of this method include (1) substantial rate acceleration relative to traditional thermal reactions, (2) good diastereoselectivities and yields for the formation of the cyclobutanone products, and (3) inverse diastereoselectivity compared with related thermal cycloadditions for many examples. These studies not only provide access to synthetically versatile cyclobutanones that cannot be prepared by traditional thermal cycloadditions but also address important mechanistic questions regarding ketene-alkene [2 + 2] cycloaddition reactions.
Cyclopropylketenes: preparation and nucleophilic additions
Allen, Annette D.,Baigrie, Lynn M.,Gong, Leyi,Tidwell, Thomas T.
, p. 138 - 145 (2007/10/02)
Phenylcyclopropylketene (4), tert-butylcyclopropylketene (5), and dicyclopropylketene (6) were formed by dehydrochlorination of the corresponding acyl chlorides by Et3N in THF, and are the first cyclopropylketenes to be isolated and purified.Reaction of 4 with n-BuLi and capture of the intermediate enolates with Me3SiCl gave the stereoisomeric silyl enol ethers c-PrCPh=C(OSiMe3)-n-Bu with a 79:21 preference for formation of the Z isomer resulting from nucleophilic attack syn to cyclopropyl, whereas the corresponding reaction of t-BuLi gave 9:91 preference for attackanti to cyclopropyl.Some isopropyl-, cyclopentyl-, and cyclohexylketenes gave comparable results.Analyses of the relative sizes of the ketene substituents in the ground state by steric parameters, and of the product stabilities by molecular mechanics, both fail to predict the observed similarities in the results with different secondary alkyl groups.The hydration reactivities of 4 and 6 show that, in neutral H2O/CH3CN, c-PrCPh=C=O is more reactive than i-PrCPh=C=O, a result ascribed as mainly due to the smaller size of cyclopropyl. c-Pr2C=C=O has the same reactivity in neutral water as Et2C=C=O, but is 22 times less reactive with acid, a result attributed to the inability of the β-cyclopropyl groups to directly stabilize the cationic transition state for protonation. Key words: cyclopropylketenes, ketenes, nucleophilic addition, hydration kinetics.
