Provided are methods of producing phosphitylated compounds, including 3'-O-phosphoramidites, comprising the step of reacting a hydroxyl-containing compound with a phosphitylating agent in the presence of a phosphitylation activator selected from the group consisting of: (1) acid-base complexes derived from an amine base of Formula II ##STR00001## wherein R.sup.3, R.sup.4, R.sup.5, R.sup.6, and R.sup.7 are independently hydrogen, C.sub.1 C.sub.10 alkyl, C.sub.3 C.sub.10 cycloalkyl, C.sub.6 C.sub.10 aryl, C.sub.7 C.sub.10 aralkyl, C.sub.1 C.sub.10 heteroalkyl, or C.sub.1 C.sub.10 heteroaryl, and at least one of R.sup.3, R.sup.4, R.sup.5, R.sup.6, and R.sup.7 is not hydrogen; (2) zwitterionic amine complexes; and (3) combinations of two or more thereof, to produce a phosphitylated compound. Further provided are methods for purifying phosphitylated compounds comprising the steps of providing a phosphitylated compound in a solution solvent, contacting said phosphitylated compound with a precipitation solvent, and precipitating said phosphitylated compound.