Synthesis of thioacetals
Various carbonyl compounds including aliphatic and aromatic aldehydes and ketones were converted to the corresponding thioacetals in high yields in the presence of a catalytic amount of hafnium trifluoromethanesulfonate. The mild conditions tolerated various sensitive functional and protecting groups and were racemization-free when applied to R-aminoaldehydes.
Y.-C. Wu, J. Zhu, J. Org. Chem., 2008, 73, 9522-9524.
Tungstophosphoric acid (H3PW12O40) was found to be an effective and highly selective catalyst for the thioacetalization of aldehydes, ketones, acetals, acylals and O,S-acetals in excellent yields in the absence of solvent. Chemoselective conversions of α- or β-diketones and a β-keto ester are described. Sterically hindered carbonyl compounds were converted to the corresponding thioacetals in refluxing petroleum ether in good yields.
H. Firouzabadi, N. Iranpoor, K. Amani, Synthesis, 2002, 59-60.
β-Keto 1,3-dithianes can be generated by the double conjugate addition of dithiols to propargylic ketones, esters and aldehydes in excellent yields. These masked 1,3-dicarbonyl systems can be converted to a range of functionalised oxygen-containing heterocycles that can be used in natural product synthesis.
M. J. Gaunt, H. F. Sneddon, P. R. Hewitt, P. Orsini, D. F. Hook, S. V. Ley, Org. Biomol. Chem., 2003, 1, 15-16.
A new procedure for the protection of aldehydes and ketones as thioacetals promoted by catalytic amount of p-toluenesulfonic acid and silica gel has been developed. This procedure offers versatility, short reaction time, excellent yield, and is easy to carry out. A simple filtration followed by removal of solvent in most cases produces pure product.
M. H. Ali, M. G. Gomes, Synthesis, 2005, 1326-1332.
Aldehydes and ketones were protected as their thioacetals in the presence of a catalytic amount of iodine. These mild reaction conditions were also applied in the transthioacetalization of O,O-acetals, O,O-ketals, O,S-acetals, and acylals.
H. Firouzabadi, N. Iranpoor, H. Hazarkhani, J. Org. Chem., 2001, 66, 7527-7529.