Study of O-Allylation Using Triazine-Based Reagents

Development of Triazinone-Based Condensing Reagents for Amide Formation

Novel triazinone-based condensing reagents have been developed. The palladium-catalyzed O-N allylic rearrangement of 2-(allyloxy)-4,6-dichloro-1,3,5-triazine and subsequent regioselective substitution using alcohols and an amine afforded chlorotriazinones, which can be readily converted using N-methylmorpholine into the corresponding condensing reagents. The condensation of carboxylic acids and amines using these reagents proceeded to afford the desired amides in good yields. In comparison with 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride, the newly synthesized triazinone-based condensing reagents exhibited higher reactivity.

Cooperation of the Neutral and the Cationic Leaving Group Pathways in Acid-Catalyzed O-Benzylation of TriBOT

The reaction profile of acid-catalyzed O-benzylation with 2,4,6-tris(benzyloxy)-1,3,5-triazine (TriBOT) was analyzed to study the reaction kinetics. The first-order kinetic constant for the formation of benzyl cation species from N-protonated TriBOT (neutral leaving group pathway) was estimated and compared with that of the model compound for TriBOT. Since rapid consumption of TriBOT in the late stage could not be explained solely by this pathway, cooperation of another reaction mechanism, the cationic leaving group pathway, was proposed to rationalize the rate acceleration.

Triazine-Based Cationic Leaving Group: Synergistic Driving Forces for Rapid Formation of Carbocation Species

A new triazine-based cationic leaving group has been developed for the acid-catalyzed alkylation of O- and C-nucleophiles. There are two synergistic driving forces, namely, stable C═O bond formation and charge-charge repulsive effects, involved in the rapid generation of the carbocation species in the presence of trifluoromethanesulfonic acid (∼200 mol %). Considerable rate acceleration of benzylation, allylation, and p-nitrobenzylation was observed as compared to the reactions with less than 100 mol % of the acid catalyst. The triazine-based leaving group showed superior p-nitrobenzylation yield and stability in comparison to common leaving groups, trichloroacetimidate and bromide. A plausible reaction mechanism (the cationic leaving group pathway) was proposed on the basis of mechanistic and kinetic studies, NMR experiments, and calculations.

Development of a method for the synthesis of 2,4,5-trisubstituted oxazoles composed of carboxylic acid, amino acid, and boronic acid

A novel method for the synthesis of trisubstituted oxazoles via a one-pot oxazole synthesis/Suzuki–Miyaura coupling sequence has been developed. One-pot formation of 5-(triazinyloxy)oxazoles using carboxylic acids, amino acids and a dehydrative condensing reagent, DMT-MM, followed by Ni-catalyzed Suzuki–Miyaura coupling with boronic acids provided the corresponding 2,4,5-trisubstituted oxazoles in good yields.