Generation and intramolecular cationic cyclizations of N-tosylimines derived from enolizable aldehydes

An Efficient and Convenient Procedure for Preparation of N-Sulfonylimines Catalysed by TiO2/SO42- Solid Superacid

A facile synthesis of N-sulfonylimines in good to excellent yields was described from aldehydes with sulfonamides catalysed by TiO2/SO42- solid superacid.

Triarylmethyl chlorides as novel, efficient, and mild organic catalysts for the synthesis of N-sulfonyl imines under neutral conditions

A highly efficient procedure for the preparation of N-sulfonyl imines via condensation of sulfonamides with aldehydes as well as ketones in the presence of triarylmethyl chlorides as metal-free organo-catalysts at 40 °C is described. The advantages of this class of catalysts over the reported ones are their efficiency and possibility of running reactions in neutral media that makes them suitable for acid-sensitive substrates.Key words: triarylmethyl chloride, N-sulfonyl imine, sulfonamide, aldehyde, ketone.

A General Method for the Preparation of N-Sulfonyl Aldimines and Ketimines

[Reaction: see text] A simple procedure to obtain N-sulfonyl imines involving the condensation of carbonyl compounds with p-tolyl or tert-butyl sulfinamides followed by oxidation with m-CPBA of the resulting N-sulfinylimines is reported. The method is applicable to aldehydes (aliphatics and aromatics) and ketones (diaryl, dialkyl, and aryl alkyl), even those containing enolizable protons. It also does not affect C=N or C=C double bonds and does not epimerize alpha-stereogenic centers.

A New, Mild Synthesis of N-Sulfonyl Ketimines via the Palladium-Catalyzed Isomerization of Aziridines

[reaction: see text] A new method for the synthesis of N-tosylketimines via the palladium-catalyzed isomerization of N-tosylaziridines is described. The mild reaction conditions tolerate the presence of a variety of functional groups including ketones, esters, and acetals. The reactions are believed to proceed via the oxidative addition of the aziridine to Pd(0) and represent the first examples of transformations involving Pd(0)-mediated oxidative additions of aziridines that do not proceed through allylpalladium intermediates.

New Lewis-Acidic Molybdenum(II) and Tungsten(II) Catalysts for Intramolecular Carbonyl Ene and Prins Reactions. Reversal of the Stereoselectivity of Cyclization of Citronellal

New Mo(II) complexes BnEt(3)N(+)[Mo(CO)(4)ClBr(2)](-) (A) and Mo(CO)(5)(OTf)(2) (B) and their W(II) congeners D and E have been developed as catalysts for the title reactions. Unlike other Lewis acids, the latter catalysts exhibit cis-stereoselectivity in the cyclization of citronellal (1 --> 3 with A and 1 --> 5 with B). Isotopic labeling allowed formulation of the reaction mechanism, according to which these complexes act as bulky Lewis acids, eta(1)-coordinated to the carbonyl oxygen. The stereochemistry appears to be controlled by the protruding ligand L(p), which dictates the boatlike transition state III. The kinetically formed cis-alkenol 3 can be equilibrated by [Mo(CO)(4)Br(2)](2) (C) or ZnCl(2) to its trans-epimer 2 via a retro-ene reaction.