Trialkylsilyl trifluoromethanesulphonates

Aza-Diels-Alder reactions, where the nitrogen is part of the diene component, have also featured prominently this year. Fowler and co-workers, in a continuation of their studies of the formation and trapping of 1-aza-dienes generated by thermal elimination of acetic acid from hydroxamic acid derivatives, have now described an application of the reaction to the total synthesis of the quino-lizidine alkaloid (-)-deoxynupharidine (288) (Scheme 25). Reaction to give (286) and (28 ) probably proceeds via exo, chair transition states where the major product (286) is derived from the transition state which has the methyl group on the connecting chain in an equatorial position. Kametani and co-workers have reported a useful extension to their earlier work on the Intramolecular aza-Diels-Alder reaction. Cycloaddition can now be carried out under much milder conditions than those previously described by using a trialkylsilyl trifluoromethanesulphonate as catalyst. BenzoCa ]-quinolizidine (290), for example, is obtained in excellent yield from the enamide (289). ... 

Two other trialkylsilyl trifluoromethanesulphonates, the TBDMS and tri-isopropylsilyl (TIPS) compounds, have been prepared and used in silylation reactions catalysed by 2,6-lutidine " TBDMS triflate allows formation of TBDMS ethers from tertiary and unreactive secondary alcohols, and TIPS triflate reacts effectively with primary and secondary alcohols. Use of the perfluorinated resin sulphonic acid trimethylsilyl ester Nafion-TMS , an immobilized TMS triflate, as a silylating agent for alcohols cf. 5,167) is discussed in a publication on applications of TMS triflate in synthesis. ... 

Allylic Alcohols. Full details have appeared of the conversion of epoxides into allylic alcohols, mediated by trimethylsilyl trifluoromethanesulphonate (Scheme 4) (see 6,163 4,145), and this sequence is mentioned in a review of trialkylsilyl perfluoroalkanesulphonates as reagents opening of an epoxide ring occurs at the more substituted centre. The use of trimethylsilyl iodide for the epoxide-allyl alcohol transformation (5, 158) is discussed in a review of the preparation and applications of this reagent. ... 

---