We have demonstrated O-benzylating abilities of both 4,6-bis(benzyloxy)-1,3,5-triazin-2(1H)-one (DiBOT) and 6-(benzyloxy)-1,3,5-triazine-2,4(1H,3H)-dione (MonoBOT), which have been previously suggested as reaction intermediates of the acid-catalyzed benzylation of 2,4,6-tris(benzyloxy)-1,3,5-triazine (TriBOT). We studied the effect on the reactivity of acid-catalyzed O-benzylation caused by the isomeric core triazine structures in these compounds by carrying out a kinetic study and estimating relative basicities using model compounds. Since MonoBOT showed superior reactivity, 1,3,5-triazine-2,4(1H,3H)-dione is a promising core structure for acid-catalyzed alkylating reagents.
A new tert-butylating reagent, 2,4,6-tris(tert-butoxy)-1,3,5-triazine (TriAT-tBu) has been developed for the acid-catalyzed tert-butylation of alcohols and carboxylic acids. The reaction of various alcohols and carboxylic acids with TriAT-tBu in the presence of a catalytic amount of an acid provided the [a] 4093 corresponding tert-butyl ethers and esters in good to high yields. TriAT-tBu is an air-stable solid synthesized in good yield from inexpensive starting materials, namely, cyanuric chloride, tBuOH, and sodium hydride. deprotection can be readily achieved under acidic conditions with the liberation of isobutene, while tert-butyl ethers are tolerated under various reaction conditions. [3] The traditional methods for preparing tert-butyl ethers and esters involve the reaction of a large excess of isobutene or tert-butyl 2,2,2-trichloroacetimidate (tert-BTCAI) in the presence of an acid catalyst. [3,4] However, handling and storage of the flammable gaseous isobutene is inconvenient and potentially hazardous, and tert-BTCAI is sensitive to moisture and heat. [5] By analogy with Tri-BOT and TriBOT-PM, a triazine-based tert-butylating reagent is expected to solve these problems.Herein, we report the development of a tert-butylating reagent, 2,4,6-tris(tert-butoxy)-1,3,5-triazine (TriAT-tBu). [6] Eur.
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.
Acid-catalyzed allylating reagent 2,4,6-tris(allyloxy)-1,3,5-triazine (TriAT-allyl) and its substituted derivatives have been developed. The reaction of acid-, and alkali-labile alcohols with these reagents in the presence of a catalytic amount of trifluoromethanesulfonic acid (TfOH) afforded the corresponding allyl ethers in good yields. Reactions using these reagents with an unsymmetrically-substituted regioisometric allyl group suggested that a single isometric allylic cation species would be involved.
A new tert‐butylating reagent, 2,4,6‐tris(tert‐butoxy)‐1,3,5‐triazine (TriAT‐tBu) has been developed for the acid‐catalyzed tert‐butylation of alcohols and carboxylic acids. The reaction of various alcohols and carboxylic acids with TriAT‐tBu in the presence of a catalytic amount of an acid provided the corresponding tert‐butyl ethers and esters in good to high yields. TriAT‐tBu is an air‐stable solid synthesized in good yield from inexpensive starting materials, namely, cyanuric chloride, tBuOH, and sodium hydride.
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