US Patent 7560555 Process for the preparation of phosphitylation agents

A process for the preparation of a compound of formula R1—Y1—P(NR2R3)2 is provided. The process comprises reacting a compound of formula PX3 with a compound of formula HNR2R3 to form a compound of formula X—P(NR2R3)2; and reacting the compound of formula X—P(NR2R3)2 with a compound of formula R1—Y1—H in the presence of a hydrocarbon solvent to form the compound of formula R1—Y1—P(NR2R3)2. R1 represents a phosphorus protecting group; R2 and R3 each independently represent an alkyl, prefer-ably a C1-6alkyl, group, or R2 and R3 are joined, together with the N to which they are attached, to form a 5-7 membered ring; Y1 represents O or S, preferably O; and X represents a halogen, preferably Cl. The preferred solvent is toluene.