Development of Triazine-Based Benzylating Reagents Possessing <i>t</i>-Butyl Group on the Triazine Core: Thermally Controllable Reagents for the Initiation of Reaction

Abstract

Benzylating reagents, 4-(4,6-di-t-butyl-1,3,5-triazin-2-yl)-4-benzylmorpholinium triflate, and related derivatives have been developed. The reagents release benzyl triflate as a benzyl cation equivalent upon heating the solution to 40°C under neutral conditions. The O-benzylation of alcohols using a stoichiometric amount of these reagents afforded corresponding benzyl ethers in good to high yields. This was due to the presence of a bulky t-butyl group on the triazine ring of these reagents that prevents the consumption of benzyl triflate via a side reaction with a morpholinotriazine derivative.

Development of a Storable Triazinone-Based Reagent forO-p-Methoxybenzylation under Mild Heating Conditions

“…The core structure 1,3,5-triazin-2­(1 H )-one, which was previously evaluated in our study on acid-catalyzed benzylating reagents, achieved the compatibility between the reactivity and stability of 1 . On the basis of our previous findings, the substituents of 1 (the tert -butyl and N -propargyl groups) were rationally designed to suppress an N -alkylating side reaction that was occasionally observed in the reaction of triazine-based alkylating reagents. ,− The sterically bulky tert -butyl group on the triazine ring effectively reduced the N -benzylating side reaction caused by benzyl cation species . In addition, the fixation of the heterocyclic core structure through the introduction of the N -substituent inhibited the side reaction that occurred via core structure isomerization during acid-catalyzed O -benzylation .…”