Amines, reaction with elemental sulfur

The reaction of phosphorus ylides with elemental sulfur gave thioaldehydes, which were trapped in situ by treatment with secondary amines to afford the corresponding thioamides (equation 17)237. 

As previously mentioned (Section III.A) the reaction of phosphonium ylides with elemental sulfur afforded thioaldehydes which, by addition of amines, yielded the corresponding thioamides237. Another application involved the reaction of cyanothioacetamide with a /J-thioxoketone to give a pyridine-2-thione217. 

Often l,2-dithiole-3-thiones are formed as by-products in reactions involving 1,2-dithiolylium salts, probably by reaction of the 1,2-dithiolylium ion with elemental sulfur from decomposition of the dithiolylium salt. With tertiary amines, 1,2-dithiolylium salts give not tetrathiafulvalenes but l,2-dithiole-3-thiones6 (e.g., la - 2). 

Sulfur diamides (diaminosulfanes) are obtained by the action of sulfur chlorides with an aliphatic secondary amine (Eq. 10.10). ° The monoselanes Se(NR2)2 (R = Me, Et) have also been prepared. Polyselanes Scx(NR2)2 (x = 2 - 4, NR2 = morpholinyl x = 4, NR2 = piperidinyl) are formed in the reaction of elemental selenium with the boiling amine in the presence of Pb304. ... 

The manufacture of sulfur dyes involves sulfurisation processes, the chemistry of which remains rather mysterious and may arguably be considered still to be in the realms of alchemy The processes involve heating elemental sulfur or sodium polysulfide, or both, with aromatic amines, phenols or aminophenols. These reactions may be carried out either as a dry bake process at temperatures between 180 and 350 °C or in solvents such as water or aliphatic alcohols at reflux or at even higher temperatures under pressure. C. I. Sulphur Black 1, for example, is prepared by heating 2,4-dinitrophenol with sodium polysulfide. 

There have been two published reports on the syntheses of stable 1,2,4-triazolyl carbenes. Thermal decomposition in vacuo of 5-methoxytriazoline 208 provided in quantitative yield l,2,4-triazol-5-ylidene 209, a stable carbene in the absence of oxygen and moisture <0381292>. This nucleophilic carbene 209 could react with a variety of alcohols, thiols, amines, oxygen, sulfur, selenium, isocyanantes, and metal carbonyls to form a myriad of addition products. Reactions of 1,2,4-triazolyl perchlorate salts 210 with base afforded stable nucleophilic 1,2,4-triazol-5-ylidenes 211, which could react with acetonitrile and elemental sulfur and selenium to yield addition products <03JOC5762>. 

Elemental selenium is an excellent catalyst for fhe carbonylation of a variety of nucleophiles such as amines, alcohols, water, and carbon nucleophiles in the presence of oxygen under mild conditions [114]. In fhe synfhesis of ureas from primary amines and CO, for example (Scheme 15.42), the turnover number reaches ca. 10", giving ureas in almost quantitative yields. Successful applications of this Se/CO system include not only synfhetic reactions with a variety of carbamates, carbonates, and sulfur- or selenium-containing compounds but also metallurgical refining of selenium and several important processes as exemplified by isocyanate synfhesis, fhe water-gas shift reaction, and separation of carbon monoxide [115]. 

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