Synthesis of alkyl 2-(2-oxo-1,2-dihydronaphtho[2,1-b]thiophen-1-yl)-2-(1,1,1-triphenyl-λ5-phosphanylidene)acetates from triphenylphosphine, acetylenic esters, and 2-naphthalenethiol

A one-pot synthesis of alkyl 2-(2-oxo-1,2-dihydronaphtho[2,1-b]thiophen-1-yl)-2-(1,1,1-triphenyl-lambda(5) -phosphanylidene)acetates in fairly high yields by the reaction of 2-naphthalenethiol, dialkyl acetylenedicarboxylates and triphenylphosphine is reported. The formulas of these compounds were confirmed by IR, H-1,P-31, and C-13 NMR spectroscopy. The NMR spectra indicated that solutions of the phosphorus ylides (CDCl3 as solvent) contain two rotamers (E and Z). The relative percentages of rotamers in CDCl3 for each phosphorus ylide were determined from the P-31 NMR spectra.