A method of deprotecting a solid support bound polynucleotide includes the step of contacting the polynucleotide with a composition comprising a diamine under conditions sufficient to deprotect the 2′-protected ribonucleotide residue. The solid support bound polynucleotide has at least one 2′-protected ribonucleotide residue, which has the following structure: wherein BP is a protected or unprotected heterocycle; R12 is a protecting group selected from a hydrocarbyl, a substituted hydrocarbyl, an aryl, and a substituted aryl; X is O or S; and PG is a thionocarbamate protecting group.