Categories: C-S Bond Formation >
Synthesis of β-sulfido carbonyl compounds and related compounds
A cinchona alkaloid-derived urea is an efficient organocatalyst for catalyzing enantioselective conjugate addition between thiols and various α,β-unsaturated ketones to provide optically active sulfides with high chemical yields and enantiomeric excess. The reaction was performed with 0.1 mol % of catalyst in toluene at room temperature.
N. K. Rana, S. Selvakumar, V. K. Singh, J. Org. Chem., 2010, 75, 2089-2091.
Efficient, asymmetric conjugate addition-protonation reactions of thiols to α-substituted vinyl ketones are catalyzed by a chiral primary-tertiary diamine derived from l-phenylalanine. This organocatalyst promotes the sulfa-Michael addition-protonation reactions with good to excellent enantioselectivity.
N. Fu, L. Zhang, S. Luo, J.-P. Cheng, Org. Lett., 2014, 16, 4626-4629.
A highly efficient organocatalytic asymmetric sulfa-Michael addition of thiols to hexafluoroisopropyl α,β-unsaturated esters performs well over a broad scope of α,β-unsaturated esters and diversified thiols. Introducing electron-withdrawing hexafluoroisopropyl ester is crucial to enhancing the electrophilicity of unsaturated esters as Michael acceptors.
X. Fang, J. Li, C.-J. Wang, Org. Lett., 2013, 15, 3448-3451.
The use of tetrabutylammonium hydroxide as an efficient thia-Michael addition catalyst enables the conjugate addition of a broad range of mercaptan nucleophile to a very wide range of both classical and non-classical Michael acceptors. This methodology is especially attractive and operationally simple, as it generally proceeds with low catalytic loading and without excess reagent, and the produced products typically require no purification.
D. R. Nicponski, J. M. Marchi, Synthesis, 2014, 46, 1725-1730.
β-Sulfido carbonyl compounds were formed at room temperature, in short times and with excellent chemoselectivity by a catalyst-free conjugate addition of thiols to ,-unsaturated carbonyl compounds in water. Competitive dithiane/dithiolane formation, transesterification, and ester cleavage were not observed.
G. L. Khatik, R. Kumar, A. K. Chakraborti, Org. Lett., 2006, 8, 2433-2436.
Tetrabutylammonium bromide is an inexpensive ionic liquid, which efficiently catalyzes the conjugate addition of thiols to α,β-unsaturated nitriles, carboxylic esters, ketones and aldehydes as well as nitro olefins.
B. C. Ranu, S. S. Dey, A. Hajra, Tetrahedron, 2003, 59, 2325-2331.
A rapid conjugate addition of thiols to α,β-unsaturated ketones is achieved in a hydrophobic ionic liquid [bmim]PF6/H2O solvent system in the absence of any acid catalyst. This mild and neutral method gave the corresponding Michael adducts in high yields with excellent 1,4-selectivity. The ionic liquid can be reused.
J. S. Yadav, B. V. S. Reddy, G. Baishya, J. Org. Chem., 2003, 68, 7098-7100.
A versatile RuCl3-catalyzed 1,4-conjugate addition of primary, secondary and aromatic amines, thiols, and carbamates to α,β-unsaturated compounds in poly(ethylene glycol) (PEG) provides the desired β-substituted carbonyls in high yields. RuCl3-PEG offers low sensitivity toward moisture and oxygen, high tolerance of different functional groups, and efficient recyclability.
H. Zhang, Y. Zhang, L. Liu, H. Xu, Y. Wang, Synthesis, 2005, 2129-2136.
S-Alkylisothiouronium salts are a nontoxic, odorless and simply operational alternative of thiols for the thia-Michael addition with electron-deficient olefins. The reactions were carried out under alkaline conditions in water at room temperature within short reaction times to afford the expected products in good yields.
Y. Zhao, Z.-M. Ge, T.-M. Cheng, R.-T. Li, Synlett, 2007, 1529-1532.
CeCl3 • 7H2O/NaI supported on neutral alumina (Al2O3) promotes heteroatom Michael additions under solvent-free conditions. The CeCl3 • 7H2O/NaI/Al2O3 system works well for hetero-Michael additions of weak nucleophiles such as imidazoles and carbamates to various acceptors.
G. Bartoli, M. Bartolacci, A. Giuliani, E. Marcantoni, M. Massaccesi, E. Torregiani, J. Org. Chem., 2005, 70, 169-174.
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.