- Systematic Evaluation of 1,2-Migratory Aptitude in Alkylidene Carbenes
-
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.
- Dale, Harvey J. A.,Nottingham, Chris,Poree, Carl,Lloyd-Jones, Guy C.
-
supporting information
p. 2097 - 2107
(2021/02/01)
-
- One-pot, modular approach to functionalized ketones via nucleophilic addition/Buchwald-Hartwig amination strategy
-
A general one-pot procedure for the 1,2-addition of organolithium reagents to amides followed by the Buchwald-Hartwig amination with in situ released lithium amides is presented. In this work amides are used as masked ketones, revealed by the addition of organolithium reagents which generates a lithium amide, suitable for subsequent Buchwald-Hartwig coupling in the presence of a palladium catalyst. This methodology allows for rapid, efficient and atom economic synthesis of aminoarylketones in good yields.
- De Jong, Jorn,Heijnen, Dorus,Helbert, Hugo,Feringa, Ben L.
-
supporting information
p. 2908 - 2911
(2019/03/17)
-
- Synthesis of diaryl ketones through oxidative cleavage of the C-C double bonds in N -Sulfonyl enamides
-
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.
- 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)
-
- Mechanistic aspects for the oxidation of brilliant green dye by chloramine-T in the presence of perchloric acid: A spectrophotometric kinetic approach
-
The kinetics of a triarylmethane dye, brilliant green (BG), by sodium N-chloro-p-toluenesulfonamide or chloramine-T (CAT) was studied spectrophotometrically in HClO4 media at 303 K. Under identical experimental conditions, the rate law was -d [BG]/dt = k [BG] [H+]. Variations in ionic strength (μ) of the medium had no effect on the oxidation velocity. Addition of p-toluenesulfonamide, the reduction product of CAT and Cl-, had no significant effect on the rate of reaction. The values of rate constants observed at five different temperatures (298, 303, 308, 313, and 318 K) were utilized to calculate the activation parameters. The observed results have been explained by a general mechanism and the related rate law has been obtained. The process demonstrated in this study is cost effective, which holds great promise in potential application for pollutant control.
- Singh, Ajaya Kumar,Bano, Shakila
-
p. 605 - 617
(2014/02/14)
-
- 2-Substituted 1,3-Benzoxathiolium Tetrafluoroborates as Efficient Acylating Agents for N,N-Dialkylarylamines
-
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.
- Cadamuro, Silvano,Degani, Iacopo,Fochi, Rita,Gatti, Antonella,Regondi, Valeria
-
p. 544 - 547
(2007/10/02)
-
