Categories: C-S Bond Formation >
Synthesis of thioesters and thioacids
An efficient, fast and convenient protocol for the synthesis of N-urethane-protected α-amino/peptide thioacids from their corresponding acids and Na2S is mediated by EDC. The chemistry is compatible with a wide variety of urethane protecting groups, side-chain functionalities, and sterically hindered amino acids.
T. M. Vishwanatha, M. Samarasimhareddy, V. V. Sureshbabu, Synlett, 2012, 23, 89-92.
A thiazolium precatalyst facilitates electrochemical oxidation of thiolate anions, leading to deleterious formation of disulfide byproducts. For the reaction of a broad range of aldehyde and thiol substrates, thioesters were obtained in very good yields . This approach provides an atom-efficient thioesterification that circumvents the need for stoichiometric exogenous oxidants, high cell potentials, or redox mediators.
K. A. Ogawa, A. J. Boydston, Org. Lett., 2014, 16, 1928-1931.
4,4′-azopyridine is a suitable electron-deficient reagent for Mitsunobu esterification and thioesterification reactions. This new reagent facilitates the isolation of its hydrazine byproduct without restricting the reaction scope. The pyridine hydrazine byproduct can be simply reoxidized. The stereochemistry of the reaction under the reported conditions is with perfect retention of configuration.
N. Iranpoor, H. Firouzabadi, D. Khalili, S. Motevalli, J. Org. Chem., 2008, 73, 4882-4887.
Reduction of ethanethiol esters of α-amino acids to α-amino aldehydes by triethylsilane and catalytic palladium-on-carbon is described. α-Amino aldehydes with Boc, Cbz, or Fmoc protection could be obtained without racemization in high yield.
H. Tokuyama, S. Yokoshima, S.-C. Lin, L. Li, T. Fukuyama, Synthesis, 2002, 1121-1123.
Diverse thiol esters were synthesized in good yields by reactions of thiophenol, benzyl mercaptan, ethyl mercaptoacetate, and mercaptoacetic acid with N-acylbenzotriazoles under mild conditions. These results demonstrate the utility of N-acylbenzotriazoles as mild S-acylating agents.
A. R. Katritzky, A. A. Shestopalov, K. Suzuki, Synthesis, 2004, 1806-1813.
The addition of 3-10 mol-% DMAP accelerates the DCC-activated esterification of carboxylic acids with alcohols and thiols to such an extent that formation of side products is suppressed and even sterically demanding esters are formed in good yields at room temperature.
B. Neises, W. Steglich, Angew. Chem. Int. Ed., 1978, 17, 522-524.
A convenient procedure allows the synthesis of esters and thioesters from the corresponding carboxylic acid using TFFH as the coupling reagent. The preparation of N-acyl-dithiocarbamates from carboxylic acids and 1,3-thiazolidine-2-thione is also described.
M. Pittelkow, F. S. Kamounah, U. Boas, B. Pedersen, J. B. Christensen, Synthesis, 2004, 2485-2492.
The facile and efficient conversion of a tert-butyl protecting group to an acetyl protecting group by catalytic amounts of bromine in acetyl chloride and the presence of acetic acid has been developed. The fairly mild reaction conditions are of particular interest for new protecting group strategies for sulfur functionalised target structures.
A. Blaszczyk, M. Elbing, M. Mayor, Org. Biomol. Chem., 2004, 2, 2722-2724.
Various alcohols, thiols, phenols, and amines can be acetylated using acetic anhydride in the presence of catalytic quantity of silver triflate. The method proceeds under mild conditions, does not involve cumbersome workup, and the resulting products are obtained in high yields within a reasonable time.
R. Das, D. Chakraborty, Synthesis, 2011, 1621-1625.
Various alcohols, phenols, amines and thiols may easily be converted into acetate derivatives by treatment with acetic anhydride in the presence of acetonyltriphenylphosphonium bromide in good yields at room temperature. With the same precatalyst, both aliphatic and aromatic aldehydes can be transformed into the corresponding gem-diacetates under reflux conditions.
A. T. Khan, L. H. Choudry, S. Ghosh, Eur. J. Org. Chem., 2005, 2782-2787.
Copper(II) tetrafluoroborate efficiently catalyzes acetylation of structurally diverse phenols, alcohols, thiols, and amines with stoichiometric amounts of Ac2O under solvent-free conditions at room temperature. Acid-sensitive alcohols are smoothly acetylated without competitive side reactions.
A. K. Chakraborti, R. Gulhane, Shivani, Synthesis, 2004, 111-115.
Acylation of alcohols, thiols, and sugars were studied with a variety of Lewis acids, and it was found that Cu(OTf)2 was very efficient in catalyzing the reaction under mild conditions in CH2Cl2.
K. L. Chandra, P. Saravan, R. K. Singh, V. K. Singh, Tetrahedron, 2002, 58, 1369-1374.