Rearrangement Trimethylsilyl trifluoromethanesulfonate

A diastereoselective synthesis of /3-(iV-acylamino)aldehydes was accomplished via ruthenium-catalyzed isomerization of 0-vinyl-iV,0-acetals followed by rearrangement in the presence of trimethylsilyl trifluoromethanesulfonate (TMSOTf) (Scheme 36).63... 

In addition to the example depicted in Scheme 20.40 and examples involving a prototropic rearrangement [61], the use of trimethylsilyl trifluoromethanesulfonate to induce the transformation of 212 afforded 213 bearing a keto substituent at the allenic terminus (Scheme 20.44) [81]. Thermolysis of 213 promoted the Myers-Saito cyclization leading to 216. 

An example that illustrates the advantages that an enol ether can offer vis-d-vis the parent carbonyl compound in iminium ion cyclization is found in Overman and Goldstein s construction of the allopumi-liotoxin A alkaloid intermediate (32). A variety of Mannich conditions failed to produce (32) from amino ketone (28), but yielded only cyclopentaoxazolidine (29). However, intramolecular Mannich cyclization was accomplished in 52% yield at low temperature by treatment of the bicyclic trimethylsilyl enol ether (30) with 1.1 equiv. of trimethylsilyl trifluoromethanesulfonate (Scheme 15). Remarkably, (32) produced in this manner was racemic, a result ascribed to facile [3,3] sigmatropic rearrangement of intermediate (31). 

An ab initio study of the Wolff rearrangement of 1,2-ketocarbene, C6H4O, in the gas phase has been undertaken, and a quantum-chemical investigation of solvent effects on the competition between the Wolff transposition (307) (308) and 1,2-H-shift process (307) (309) in /3-hydroxyketocarbenes has been carried out. It has been found that in the reaction of a-diazo esters with aldehydes in the presence of a stoichiometric amount of trimethylsilyl trifluoromethanesulfonate, 1,2-nucleophilic rearrangement of the substituent derived from the aldehyde is favoured, resulting in the... 

Novel secosteroids (336) and (337) have been prepared from the acid-catalysed rearrangements of fluocinonide acetonide (335 R = H) in the presence of trifluoro-methanesulfonic anhydride and trimethylsilyl trifluoromethanesulfonate as catalyst see... 

Ring expansion of keto aziridines to the 2,5-diaryloxazoles in the presence of dicyclohexyl carbodiimide and iodine has been reported. A tandem thia-Fries rearrangement of 2-(trimethylsilyl)phenyl trifluoromethanesulfonate aryne precursors has been described (Scheme 76). ° ... 

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