Alkynyl thiocyanates

Alkynyl thiocyanates Alkynyl thiotosylates Alkynyl phosphorodithioates... 

High density brine completion fluids also often require the use of corrosion inhibitors (8,9). Blends of thioglycolates and thiourea alkyl, alkenyl, or alkynyl phosphonium salts thiocyanate salts mercaptoacetic acid and its salts and the reaction products of pyridine or pyrazine derivatives with dicarboxylic acid monoanhydrides have been used as high density brine corrosion inhibitors. 

Thiols react directly with non-activated alkynes [15] and with 1-alkynyl thioethers [16] to yield alkenyl thioethers in good yield (>76%), whereas thiocyanate anions only add to non-activated alkynes under acidic phase-transfer catalytic conditions on the addition of mercury(II) thiocyanate. Terminal alkynes are converted into vinyl thiocyanates, but disubstituted alkynes also form vinyl isothiocyanates [17]. Major by-products are the ketones formed by solvolysis of the alkynes. 

Preparation of 1-Alkynyl Thiocyanates from ADcynethiolates and Cyanogen Chloride Et20-hexane... 

Thiocyanation was very effective with several alkynyl iodonium salts, in a simple process avoiding the previously used cyanogen chloride or mercury compounds best yields of alkynyl thiocyanates were obtained using potassium thiocyanate in DMF [66],... 

The propensity of the thiocyanate ion for alkynylation with alkynyliodonium ions has also been demonstrated with a series of bis(phenyliodonium)diyne triflates (equations 61 and 62)43. The efficient production of diynediyl dithiocyanates in these reactions may be contrasted with the favored formation of mono- and bis-cyclopentenyl sulfones from bisiodonium diyne salts and sodium/ -toluenesulfinate (see equation 57)86. 

Reaction of 1-alkynyl thiocyanates (300) with alcohols, phenols, thiols, or secondary aliphatic amines in the presence of a Lewis acid (anhydrous zinc chloride or boron trifluoride diethyl etherate) affords 2,4-disubstituted thiazoles (301) in good yields (Equation (52)) <82RTC310>. 

A wide variety of sulfur nucleophiles react readily with alkynyliodonium salts. Reaction with sodium thiocyanate in aqueous CH2CI2 afforts alkynyl thiocyanates, 82, in 70-94170 yields [Eq. (38)] [65]. Similarly, diyne dithiocyanates, 83 and 84, are obtained in 69-80% yield from reaction of 34 and 35 with NaSCN [Eqs. (39) and (40)], respectively [41]. Litewise, alkynyl thiocyanates, 82, are obtained from 23 and KSCN in DMF [Eq. (41)] [66]. 

The alkynylation of sulfur nucleophiles works well with alkynyliodonium tosylates and triflates as long as the sulfur atom is not too electron-rich, else oxidation reactions dominate. For example, alkynyl thiocyanates [38, 39, 75], thiotosylates [76], and phosphorodithioates [77] can be accessed in good yields (Scheme 8, A). The alkynylation of thioamides is also possible, but in this case the product obtained is imstable and spontaneously cyclizes to give a thiazole (Scheme 8, B) [78, 79]. The alkynylation of sulfinates with alkynyliodOTiium triflates or tosylates gives an efficient access towards alkynyl sulfones (Scheme 8, C) [80, 81]. If C-H bonds are easily accessible, carbene C-H insertion products can... 

Stepwise addition of sulphur and cyanide to acetylides provides 1 -alkynyl thiocyanates (21) they may be used for introduction of an RC=C—S— unit, as in the preparation of the previously unknown JViV-dialkylalk-1-ynesulphenamides (22). ... 

Differences between cyanide and acetylide complexes arise from the instability of the acetylide ligand to hydrolysis. The alkynyl anions are strong bases, and anhydrous solvents such as liquid ammonia must be used in the preparation of many of their complexes. Metal thiocyanates,... 

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