Iso thio-cyanates

Figure 6.51 Biflinctional (thio)urea-phoshine catalysts 166-168 prepared from (R)-2 -diphenylphosphanyl- [1,1 ]binaphthalenyl-2-ylamine and the corresponding iso(thio) cyanate the yield of the catalysts is given in parentheses. Catalyst screening results ofthe...

Azolines of type (13) undergo thermal decomposition in an analogous way to that already discussed for azolones (see Section 4.14.5.2) (Scheme 19). Path (i) is followed by those azolines having Z = S and path (ii) by those with Z = O. Path (i) is a typical retro-1,3-dipolar cycloaddition process, via an intermediate nitrile sulfide, while path (ii) might involve an acyl (Y = Z = O) or thioacyl (Y = S, Z = O) nitrene intermediate (136), which in turn rearranges to iso(thio)cyanate. However, no systematic attempts to trap this possible nitrene intermediate seem to have been made, and so a concerted pathway for the fragmantation cannot be ruled out. 

Mesoionic pyrido[2,l- >][1,3]oxazines (54) afforded 4-oxo-4//-pyrido[l,2-a]pyrimidin-l-iumolates (55) and 4//-quinolizin-4-one (56) with phenyl iso(thio)cyanates [78LA1655 79CB1585 82ZN(B)222] and dimethyl acetylenedicarboxylate (79CB1585), respectively. Reaction of 2-cyano-3-methyl-lH,6//-pyridol[l,2-a][3,l]benzoxazine-l,6-dione with ammonium acetate and hydroxylamine, hydrazines, primary aliphatic or aromatic amines, and (thio)ureas gave 5-unsubstituted and 5-substituted 2-cyano-3-methyl-l//,6H-pyrido[l,2-a]quinazoline-l,6-diones (93CCC1953). 

The isomerism existing in the case of cyanides or nitriles and isocyanides or iso-nitriles, which we have just discussed, is found also, in part, in their oxidation products the iso-cyanates and in analogous sulphur compounds the thio-cyanates and iso-thio-cyanates. We have referred to the fact that hydrocyanic acid like hydrochloric acid yields an oxygen acid which though unknown itself is represented by well known salts. 

Alkyl Thio-cyanates Alkyl Iso-thio-cyanates.—In the alkyl derivatives of thio-cyanic acid we again have isomerism exactly analogous to that in the unknown cyanates and the known iso-cyanates. 

Allyl Cyanide, Iso-thio-cyanate, etc.—From allyl chloride or the iodide there may be prepared by the customary reactions allyl cyanide and other of the cyanogen compounds. With potassium cyanide allyl iodide yields allyl cyanide. The reaction, however, instead of yielding a cyanide of the expected constitution is accompanied by a shifting of the double bond to the second carbon so that the cyanide has a constitution unlike that of the iodide from which it is made. 

Oil of Mustard.—Only the last compound named is important, viz., allyl iso-thio-cyanate, CH2 = CH—CH2NCS. Strange as it may seem, from statements made in connection with the cyanates and iso-cyanates of the saturated series, this compound is made by treating allyl-iodide, not with silver thio-cyanate, but with potassium thio-cyanate. As, however, the tautomeric iso-compounds are made from the cyanates and thio-cyanates by heat, the conversion of the first formed thio-cyanate into the iso-thio-cyanate can readily be understood. 

Allyl iso-thio-cyanate is found in nature as a glucoside constituent of mustard seed. It is known, therefore, as mustard oiL It is a liquid with a sharp odor and with a boiling point of 150.7 . The proof that it is iso-thio-cyanate is its conversion into allyl-amine, CH2 = CH—CH2NH2. 

Iso-thio-cyanates.—Isomeric with the thio-cyanic acid would be iso-thio-cyanic acid which if analogous in constitution to the iso-cyanic acid should have the constitution H—N = C = S. Neither this compound nor metal salts of it are known but alkyl derivatives are known as constituents of oil of mustard (p. 165). 

This reaction does not take place with aromatic amines. With aniline, for example, there is obtained instead a compound known as di-phenyl thio-urea, hydrogen sulphide being eliminated. On heating the diphenyl thio-urea with acids one molecule of aniline is lost and phenyl iso-thio-cyanate is obtained (p. 421). 

Nitriles from Iso-thio-cyanates.— The nitriles may also be made from iso-thio-cyanates (p. 73). When these are heated with copper the sulphur is eliminated and the iso-cyanides ox iso-nitriles are obtained and these iso-cyanides are transformed into the cyanide or nitrile. 

Cycloaddition of 2-(dicyanomethylene)piperidine with iso(thio) cyanates afforded 3-imino-4-cyano-2,3,5,6,7,8-hexahydro-l//-pyrido[l,2-c]pyrimidin-l-ones or -1-thiones (198, = H, X = O or S) (78MI1). When... 

Heating ethyl 3-aminopyridine-2-carboxylate with methyl or phenyl iso(thio)cyanate in pyridine gives the corresponding 3-substituted 2-sulfanylpyrido[3,2- ]pyrimidin-4(3//)-ones.430... 

The reaction of iminophosphorane (264) with aromatic iso(thio)cyanates leads to anhydro 2-arylamino-5-phenyl-thiazolo[2,3-h][l,3,4]thiadiazol-4-ium hydroxides (54) which upon treatment with tetrafluoroboric acid give the corresponding 2-arylamino-5-phenylthiazolo[2,3-h][l,3,4]-thiadiazolium tetrafluoroborates (53) (Scheme 25) <92T1282>. 

Reaction of the functionalized pyrimidine 266 with phenyl iso(thio)cyanate afforded pyrimido[4,5-J]pyrimidines 664 and 665 in 84% and 80% yields, respectively (Scheme 129) (04TL2405). 

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