18127-87-2Relevant articles and documents
Systematic Evaluation of 1,2-Migratory Aptitude in Alkylidene Carbenes
Dale, Harvey J. A.,Nottingham, Chris,Poree, Carl,Lloyd-Jones, Guy C.
supporting information, p. 2097 - 2107 (2021/02/01)
Alkylidene carbenes undergo rapid inter- and intramolecular reactions and rearrangements, including 1,2-migrations of β-substituents to generate alkynes. Their propensity for substituent migration exerts profound influence over the broader utility of alkylidene carbene intermediates, yet prior efforts to categorize 1,2-migratory aptitude in these elusive species have been hampered by disparate modes of carbene generation, ultrashort carbene lifetimes, mechanistic ambiguities, and the need to individually prepare a series of 13C-labeled precursors. Herein we report on the rearrangement of 13C-alkylidene carbenes generated in situ by the homologation of carbonyl compounds with [13C]-Li-TMS-diazomethane, an approach that obviates the need for isotopically labeled substrates and has expedited a systematic investigation (13C{1H} NMR, DLPNO-CCSD(T)) of migratory aptitudes in an unprecedented range of more than 30 alkylidene carbenes. Hammett analyses of the reactions of 26 differentially substituted benzophenones reveal several counterintuitive features of 1,2-migration in alkylidene carbenes that may prove of utility in the study and synthetic application of unsaturated carbenes more generally.
Synthesis of diaryl ketones through oxidative cleavage of the C-C double bonds in N -Sulfonyl enamides
Kim, Hyunseok,Park, Sangjune,Baek, Yonghyeon,Um, Kyusik,Han, Gi Uk,Jeon, Da-Hye,Han, Sang Hoon,Lee, Phil Ho
, p. 3486 - 3496 (2018/04/14)
An oxidative cleavage of a C-C double bond is developed from the photochemical [2+2]-cycloaddition of diaryl N-tosyl enamides, aryl heteroaryl N-tosyl enamides, and N-tosyl cyclic enamides with singlet molecular oxygen, followed by a ring-opening reaction mediated by Cs2CO3 under air and sunlight without the use of photosesitizer, producing symmetrical and unsymmetrical diaryl, heterodiaryl, and cyclic ketones in good to excellent yields. Moreover, the oxidative cleavage of C-C triple bonds from 1-alkynes is demonstrated for the synthesis of symmetrical and unsymmetrical ketones from the Cu-catalyzed [3+2]-cycloaddition, Rh-catalyzed alkoxyarylation, photooxygenation, and ring-opening reaction in one-pot. Because the synthesis of the symmetrical and unsymmetrical diaryl and/or heterodiaryl ketones bearing an electron-donating group is not easy, the present method is notable.
2-Substituted 1,3-Benzoxathiolium Tetrafluoroborates as Efficient Acylating Agents for N,N-Dialkylarylamines
Cadamuro, Silvano,Degani, Iacopo,Fochi, Rita,Gatti, Antonella,Regondi, Valeria
, p. 544 - 547 (2007/10/02)
2-Substituted 1,3-benzoxathiolium tetrafluoroborates were used as efficient masked acylating agents for N,N-dialkylarylamines in a two-step reaction.In most of the cases intermediate 2,2-disubstituted 1,3-benzoxathioles were obtained in high yields (about 90percent) and their hydrolysis afforded the corresponding ketones in almost quantitative yields.The new procedure offers the following advantages: (1) the reaction conditions are mild; (2) the acylation proceeds selectively at the para-position as referred to the dialkylamino group; (3) the introduction of a tertiary group is easily accomplished.
