Categories: C-S Bond Formation >
Synthesis of thiocyanates
A practical, rapid, and efficient microwave (MW) promoted nucleophilic substitution of alkyl halides or tosylates with alkali azides, thiocyanates or sulfinates in aqueous media tolerates various reactive functional groups.
Y. Ju, D. Kumar, R. S. Varma, J. Org. Chem., 2006, 71, 6697-6700.
A novel and highly selective method uses triphenylphosphine, diethylazodicarboxylate and NH4SCN for the conversion of alcohols, thiols, carboxylic acids, silyl ethers, and silyl carboxylates to their corresponding thiocyanates.
N. Iranpoor, H. Firouzabadi, B. Akhlaghinia, R. Azadi, Synthesis, 2004, 92-96.
SO2F2 promotes a one-step synthesis of thiocyanates through C-O bond cleavage of readily available alcohols with ammonium thiocyanate as the thiocyanating agent. A borad range of alcohols reacted with high efficiency in ethyl acetate under mild conditions to afford the corresponding thiocyanates in very good yields with broad functional group compatibility.
G. Zhang, L. Xuan, Y. Zhao, C. Ding, Synlett, 2020, 31, 1413-1417.
Ionic liquids [bmim][X] (X = Cl, Br, I, OAc, SCN) are highly efficient reagents for nucleophilic substitution reactions of sulfonate esters derived from primary and secondary alcohols. The newly developed protocol is very environmentally attractive because the reactions use stoichiometric amounts of ionic liquids as sole reagents without additional solvents and activating reagents. Moreover, these ionic liquids can be readily recycled.
Y. Liu, Y. Xu, S. H. Jung, J. Chae, Synlett, 2012, 23, 2663-2666.
A cross-coupling reaction of arylboronic acids with KSCN salt to yield aryl thiocyanates is catalyzed by copper acetate in the presence of 4-methylpyridine serving both as ligand and base under 0.2 MPa of molecular oxygen. Various arylboronic acids were suitable under the reaction conditions.
N. Sun, H. Zhang, W. Mo, B. Hu, Z. Shen, X. Hu, Synlett, 2013, 24, 1443-1447.
Various aromatic and heteroaromatic compounds have been efficiently thiocyanated by using a combination of bromodimethylsulfonium bromide (BDMS) and ammonium thiocyanate.
D. S. Bhalerao, K. G. Agamanchi, Synlett, 2007, 2952-2956.
A stereoselective gold-catalyzed hydrothiocyanation of haloalkynes provided vinyl thiocyanates in good yields. Furthermore, a sulfur-based gold catalyst (PPh3AuSCN) has shown a unique reactivity in gold-catalyzed reactions such as the cyclization of N-propargylic amides.
X. Zeng, B. Chen, Z. Lu, G. B. Hammond, B. Xu, Org. Lett., 2019, 21, 2772-2776.
Individual β-hydroxy thiocyanates can be synthesized in high yield and with more than 90% regioselectivity in the presence of phenol-containing macrocyclic diamides under mild reaction conditions. The method offers high regioselectivity, simple regeneration/reuse of catalyst through several cycles without a decrease in activity, and ease of workup of the reaction.
H. Sharghi, M. A. Nasseri, K. Niknam, J. Org. Chem., 2001, 66, 7287-7293.
A simple and efficient FeCl3-mediated method for the α-thiocyanation of ketones produces α-oxo thiocyanates in very good yields and with high selectivity under mild conditions. The use of inexpensive and readily available iron(III) chloride makes this procedure simple, convenient and practical.
J. S. Yadav, B. V. S. Reddy, U. V. S. Reddy, D. N. Chary, Synthesis, 2008, 1283-1287.
A mild and environmentally friendly visible-light-mediated additive-free decarboxylative functionalization of acrylic acids in the presence of ammonium thiocyanate, the inexpensive organic dye 9,10-dicyanoanthracene as a photocatalyst, and dioxygen as both an oxygen source and an oxidant provides a series of important α-thiocyanate ketones.
Z.-L. Wang, J. Chen, Y.-H. He, Z. Guan, J. Org. Chem., 2021, 86, 3741-3749.
A mild oxidation of selected anions (N3-, SCN-, I-, and Br-) by ceric ammonium nitrate (CAN) in the presence of substituted cyclopropyl alcohols provides β-functionalized ketones in short reaction times. This method provides an alternative pathway to important starting materials and intermediates in organic synthesis.
J. Jiao, L. X. Nguyen, D. R. Patterson, R. A. Flowers II, Org. Lett., 2007, 9, 1323-1326.
Anhydrous FeCl3 oxidizes potassium thiocyanate to the corresponding radical and promotes subsequent addition to nucleophilic olefins to produce dithiocyanate derivatives under mild conditions with excellent yields and chemoselectivities. The use of ferric chloride makes this method simple, convenient and practical.
J. S. Yadav, B. V. S. Reddy, M. K. Gupta, Synthesis, 2004, 1983-1986.
A 1,2-thiocyanatosulfonation of terminal alkynes with NH4SCN and sulfonyl hydrazides provides (E)-β-(thiocyanato)vinyl sulfones via a radical pathway. This metal-free reaction offers mild conditions, readily available reagents, a broad substrate scope, good functional group compatibility, and excellent stereoselectivity.
M. Zhang, X. Zeng, Org. Lett., 2021, 23, 3326-3330.