Twelve-membered B2Si4O6 borasiloxane macrocycles

A one pot three component reaction of boric acid, diphenylsilanediol and functionalized alcoholic pyrazole in 1:1:1 stoichiometry using toluene as a solvent under reflux conditions afforded twelve-membered borasiloxane macrocycle [(Ph2Si)4(O)6(BR1PzR)2] {R1 = C6H4OH and R = H for 1, R1 = C6H4OH and R = CH3 for 2 R1 = C10H6OH and R = H for 3} in moderate yields. Single crystal X-ray elucidation revealed the formation of a puckered twelve-membered ring system. ESI-MS studies indicate the stability of these macrocyclic systems in solution.