ON THE SEARCH FOR THE REGIOSELECTIVE PHOSPHORYLATION OF 1,2,4-TRIAZINES BY CYCLIC, ACYCLIC PHOSPHITES AND TRIPHENYLPHOSPHINE

Abstract

3-Triazine derivatives 1a and 1b react with phosphorus (III) reagents, to give regioselectively phos-phorylated products at C-3 or N-2 depending on the nature of the substituent at C-3 and the phosphorus reagent used. 3-chlorotriazine 1a reacts with cyclic phosphites 2a,b, and acyclic phosphites 3a-c to give the phosphonate products 6 and 10, respectively. On the other hand, reaction of 1a with 2c leads to the formation of its 3-dimethylamino-derivative 8. Reaction of 1a with triphenylphosphine gave the phosphonium salt 11. Solvolysis of 11 with aqueous methanol gave 3-hydroxytriazine 1b and triphenylphosphine. Treatment of 3-hydroxy-triazine 1b with 2-chloro-1,3,2-dioxaphospholane 2d results in formation of phosphoramidite 12 at the N-2.

Key Words:

• 1,2,4-Triazines
• cyclic phosphites
• trialkyl phosphites
• triphenylphosphine