Aspects of some alkylation reactions
Friedel-Crafts reactions of the (-)-8-phenylmenthyl and (+ )-trans-2-(acumyl) cycJohexyl aryl hydroxy acetates catalysed by trimethylsilyl triflate (TMSOTf) and equivalents in the presence of electron rich heterocycles gave the expected diarylacetates in high de 88%, via a planar cation. The interaction of trifluoromethanesulfonic (triflic) acid (TfOH) with either bistrimethylsilyl -acetamide (BSA) or -urea (BSU) can be used to generate stoichiometric amounts of trimethylsilyl triflate (TMSOTf) "in situ" , the system can be used efficiently to remove triflic acid from TMSOTf and to generate catalytic amounts of TMSOTf from TfOH for use in a range of trimethylsilyl triflate (TMSOTf) catalysed reactions. Similarly the interaction of fluorosulfonic acid (FSA) with either bis-trimethylsilyl -acetamide (BSA) or -urea (BSU) can be used to generate catalytic amounts of trimethylsilylfluorosulfonate (TMSOFs) "in situ" for use in a wide range of reactions as an alternative to trimethylsilyltriflate (TMSOTf) Scandium(III) trifluoromethanesulfonate and copper(II) trifluoromethanesulfonate can be used to catalyse aromatic alkylation with arylhydroxyacetates. Scandium(III) trifluoromethanesulfonate also proved to be a recyclable catalyst for these reactions. A number of Pictet-Spengler cyclisation reactions were also catalysed by Scandium(III) trifluoromethanesulfonate and copper(II) trifluoromethanesulfonate. Mannich reactions of a number of caJix[4jresorcinarene derivatives with (R)-(+)-amethylbenzylamine under alkaline conditions lead to the formation of single diastereomeric tetrakis(l,3-dihydrobenzoxazine) derivatives in high yields; the reactions using the (S)-(-)-a-methylbenzylamine afford the enantiomers. The products react with protic acids to afford equilibrium mixtures of diastereomers.