p-toluenesulfonyl isocyanate

Abstract

(A) Murai and co-workers showed that nucleophilic attack by TsNCO at the central carbon of a platinum π-allyl system leads to the substitution of the oxygen atom by the p-toluenesulfonyl N group in high yield. This was the first example of stoichiometric nucleophilic substitution at a central p-allyl carbon. (B) Willis et al. used TsNCO to react with mononuclear iron η1-allyls, propargyls and allenyls and afford [2+3] cycloaddition products. The iron allenyl system gave the cycloadduct shown. (C) Supuran et al. showed that the reaction of TsNCO with primary amines, amino acids or dipeptides afforded a novel class of compounds that possess powerful antitumor activity. Some functional groups had to be protected in order to avoid unwanted reactions. The product 4-toluenesulfonylureido derivatives were obtained in yields varying from 36% up to 95%. Secondary amines were reacted with TsNCO in a similar manner by Nussbaumer et al. to target several hormone dependant diseases. (D) McFarland and co-workers reported the use of TsNCO in a ring enlargement process (from 3- to 5-membered). TsNCO cyclised with an epoxide to give the corresponding toluenesulfonyl 2-oxazolinone. One of the C-O bonds of the epoxide is broken during the process and the N-C group from the tosyl isocyanate is inserted. The less sterically hindered isomer I is favoured over II. (E) Holmes et al. reported that the thermal reaction of methyl glyoxylate with TsNCO gave an imino ester via [2+2] cycloaddition, followed by cycloreversion with expulsion of carbon dioxide. (F) Sharpless and Xu reported that the reaction of an ene diol with TsNCO, catalysed by Pd(0), afforded enantiomerically enriched oxazolidin-2-ones via [2+3] cycloaddition.