“…All reagents and solvents were of analytical grade, obtained from commercial suppliers and used without further purification. Propargyl carbonate ( 1b ),48 oct‐1‐yn‐3‐yl 4‐methylbenzenesulfonate ( 4c ),49 oct‐1‐yn‐3‐yl acetate ( 4d ),50 1‐chlorobut‐2‐yne ( 9a) ,51 but‐2‐yn‐1‐yl methyl carbonate ( 9b ),48 (3‐chloroprop‐1‐yn‐1‐yl)benzene ( 10a ),52 methyl (3‐phenylprop‐2‐yn‐1‐yl) carbonate ( 10b ),53 3‐chloro‐3‐methylbut‐1‐yne ( 11a ),54 methyl (2‐methylbut‐3‐yn‐2‐yl) carbonate ( 11b ),55 1‐chloro‐1‐ethynylcyclohexane ( 12 ),56 4‐chloro‐4‐methylpent‐2‐yne ( 15a ),57 ethyl methylphosphinate ( 18 ),58 ethyl phenylphosphinate (19) ,59 ethyl (3‐methylbut‐2‐en‐1‐yl)phosphinate ( 20 ),60 5′‐ O ‐(4,4′‐dimethoxytrityl)thymidin‐3′‐yl 3′‐ O ‐ tert ‐butylsilylthymidin‐5′‐yl H‐phosphonate ( 35 ),61 diethyl H‐phosphonothioate ( 41 ),62 5′‐ O ‐(4,4′‐dimethoxytrityl)thymidin‐3′‐yl 3′‐ O ‐(4,4′‐dimethoxytrityl)thymidin‐5′‐yl H‐phosphonothioate ( 42 ),63 and 5′‐ O ‐(4,4′‐dimethoxytrityl)thymidin‐3′‐yl 3′‐ O ‐(4,4′‐dimethoxytrityl)thymidin‐5′‐yl H‐phosphonoselenoate ( 43 )64 were prepared according to published procedures. THF was dried using a VAC solvent purifier system.…”