Wei-Qiang Fan

Sulfonyl derivatives of benzotriazole: Part 1. A novel approach to the activation of carboxylic acids

Abstract 1-Acylbenzotriazoles (8, R = Me, Et, n-Bu and Ph) are prepared in good yields by fusion of benzotriazole and acid chlorides at 80 – 100°C. In cases when the corresponding acid chlorides are not available, 1-acylbenzotriazoles are conveniently available from 1-(1-methanesulfonyl)benzotriazole and the respective carboxylic acids as illustrated by the preparation of 2-, 3-, and 4-pyridoyl-, 2-pyrrolylcarbonyl- and 2-furoyl-benzotriazole in yields of 80 – 95%. Preparations of two sulfonyl derivatives of benzotriazole are also described.

Carbon dioxide: a reagent for the simultaneous protection of nucleophilic centres and the activation of alternative locations to electrophilic attack. : Part III. A new synthetic method for the ortho-subttitution of N-monoalkylanilines

Abstract N-Methyl- and M-ethyl-aniline are regiospecifically converted into a range of ortho-substituted derivatives, using carbon dioxide both for M-protection and as an intermediate carbanion stabilizing group, and t -butyllithium to lithiate the ortho-carbon atom. The resulting lithium N-(ortho-substituted-phenyl)-N-methyl- and -N-ethyl-carbamates undergo smooth acid-catalysed decarboxylation under mild conditions. No alpha-substituted products were detected.

Mechanisms and Rates of the Electrophilic Substitution Reactions of Heterocycles

The mechanisms and rates of electrophilic substitution reactions, especially acid catalyzed hydrogen exchange and nitration, of heterocycles are discussed

Acetals and ketals of 2-(2-pyridyl)propane-1,3-diol novel protection for carbonyl groups

Abstract Aldehydes and ketones are readily converted into the corresponding 1,3-dioxanes by treatment with 2-(2-pyridyl)propane-1,3-diol. The protective group is easily removed under mild base conditions after activation by quaternization with methyl iodide.

Carbon Dioxide: A Reagent for the Simultaneous Protection of Nucleophilic Centres and the Activation of Alternative Locations to Electrophilic Attack.

Abstract 2-Pyridone, using the one-pot protection method, is lithiated specifically in the 4-position. In this way, a range of 4-substituted 2-pyridones was prepared. Their orientation of substitution was proved by X-ray analysis

Carbon dioxide : a reagent for the simultaneous protection of nucleophilic centers and the activation of alternative locations to electrophilic attack. XVI, A novel synthetic method for the side-chain functionalization of N-methyl-o-toluidine and for the preparation of 2-substituted N-methylindoles

N-Methyl-o-toluidine is readily converted into a range of side-chain functionalized derivatives in a one-pot sequence, using carbon dioxide for N-protection. The intermediate lithium carbamate is further lithiated by butyllithium at the side-chain methyl group, and then reacted with an electrophile; the product undergoes acid-catalyzed decarboxylation during work-up. 2-Substituted N-methylindoles are produced when carboxylate esters are used as electrophiles. The yields are good, and no ring-substituted products are detected

Novel preparation of polyfluoroalkyl secondary and tertiary amines

Abstract Primary and secondary amines condense with benzotriazole and a polyfluoroaldehyde to give products which are reduced by sodium borohydride to give the corresponding secondary and tertiary amines containing polyfluoroalkyl groups.

Nonbonded interactions. The influence of lone pair repulsions on bond lengths

Nonbonded lone-pair repulsions are postulated as the cause of bond lengthening in isatin and a variety of other small molecules.

A mechanistic study of the rearrangement of 1-benzoyloxybenzotriazoles to 3-benzoylbenzotriazole 1-oxides

Crossover experiments demonstrate that the title rearrangement processes are intermolecular.

Studies on the thermal isomerization of N-arylmethylbenzotriazoles

The thermal isomerizations of N-benzyl-, N-diarylmethyl- and N-trityl-benzotriazole, and of N-[bis-(4-methoxyphenyl)methyl]- and N-trityl-5,6-dimethylbenzotriazole under nitrogen have been investigated. In all these cases, the N-1 isomer predominates over the N-2 isomer at thermodynamic equilibrium, to an extent which depends on the steric bulk of the N-substituent. The rate of attainment of equilibrium depends on the electronic effects of the substituents, both in the benzotriazole ring and in the migrating group. These results, in conjunction with a cross-over experiment, support a mechanism involving a heterolytic N–C bond cleavage followed by an intermolecular rearrangement.