Thiocyanato-, reactions

A-4-Thiazoline-2-ones and ring substituted derivatives are usually prepared by the general ring-closure methods described in Chapter II. Some special methods where the thiazole ring is already formed have been used, however. An original synthesis of 4- 2-carboxyphenyl)-A-4-thiazoline-2-one (18) starting from 2-thiocyanato-2-halophenyl-l-3-indandione (19) has been proposed (Scheme 8) (20, 21). Reaction of bicyclic quaternary salts (20) may provide 3-substituted A-4-thiazoline-2-one derivatives (21) (Scheme 9) (22). Sykes et al. (23) report the formation of A-4-thiazoline-2-ones (24) by treatment ef 2-bromo (22) or 2-dimethylaminothiazole (23) quaternary salts with base (Scheme 10). 

Purine, 9- -D-ribofuranosyl-6-selenoxo- 1,6-dihydro-synthesis, 5, 597 Purine, 6-thiocyanato-acylation, 5, 559 Purine, 2-thioxo-synthesis, 5, 589 Purine, 8-thioxo-iodination, 5, 559 synthesis, 5, 577, 597 Purine, 2-thioxo-2,3-dihydro-synthesis, 5, 572 Purine, 6-thioxo-1,6-dihydro-acylation, 5, 559 dethiation, 5, 558 halogenation, 5, 559 hydrolysis, 5, 560 methylation, 5, 535 oxidation, 5, 560 synthesis, 5, 572, 596 Purine, 8-thioxo-7,8-dihydro-acylation, 5, 559 Purine, 2,6,8-trichloro-alkylation, 5, 530 amination, 5, 562 reactions, 5, 561, 562 with hydriodic acid, 5, 563 with pyridine, 5, 562 synthesis, 5, 598 Purine, 2,6,8-trichloro-7-methyl-synthesis, 5, 557 Purine, 8-trifluoromethyl-synthesis, 5, 574... 

Product 15 was eventually transformed into methyl 4,6-dideoxy-a-D-xylo-hexopyranoside by reductive desulfurization. A related reaction is the formation (41) of the 4-thiocyanato derivative 17 in 47% yield from 16 (140°C., 22 hours in N,N-dimethylformamide). This has been suggested as a good route to 4-deoxy-D-xt/Zo-hexoses compared with the available methods (43). 

The reactivity at the C-4 position of hexose and hexoside sulfonates has been demonstrated in the gluco and galacto series and could undoubtedly be extended to other sugars as well. In another example (25), methyl 2,3-di-0-benzoyl-4-0-p-tolysulfonyl-a-D-glucopyranoside (18a) was treated with potassium thiocyanate in N,N-dimethylformamide at 140°C. for 9 hours to give the C-4 epimeric thiocyanato derivative 19 in 34% yield. The corresponding 4-p-bromobenzenesulfonate (18b) however, afforded a 55% yield of 19 in only 2% hours of reaction time. 

Borane, 1-methylbenzylaminocyanohydropyrrolyl-, 3, 84 Borane, thiocyanato-halogenohydro-, 3,88 Borane, trialkoxy-amine complexes, 3, 88 Borane, triaryl-guanidine complexes, 2,283 Borane, trifluoro-complexes Lewis acids, 3,87 van der Waals complexes, 3, 84 Borane complexes aminecarboxy-, 3,84 aminehalogeno-, 3, 84 amines, 3, 82, 101 B-N bond polarity, 3, 82 preparation, 3, 83 reactions, 3, 83 bonds B-N, 3, 88 B-O, 3, 88 B-S, 3, 88 Jt bonds, 3, 82 carbon monoxide, 3, 84 chiral boron, 3, 84 dimethyl sulfide, 3, 84 enthalpy of dissociation, 3, 82... 

Palladium, (diammine)bis(thiocyanato)-isomerism, 1, 185 Palladium, dichlorobis(amine)-substitution reactions stereochemistry, 1, 318 Palladium, dichlorobis(pyridine)-substitution reactions, 1, 314 Palladium, dinitritobis(triisopropylphosphine)-substitution reactions, I, 314 Palladium, ethylene-synthesis... 

The reaction of compounds 161 with bromine followed by treatment with potassium thiocyanate affords 5-thiocyanato-6-arylimidazo[2,l-A][l,3,4]thiadiazoles 163 (Equation 4) <2000EJM853>. 

Emam et al. elaborated <1997PS37> a new route to thiadiazoloquinazolones 365 by reacting the thiocyanato ketone 364 with o-ethoxycarbonylphenyldiazonium salt. The reaction was carried out at low temperature (0-5 °G) and yielded product 365. A similar reaction with a selenocyanate starting compound afforded the analogous... 

However, if reaction went by way of aquation to an aquo complex and then anation of the aquo complex to the thiocyanato, and we knew this rate constant, then the optical density would do the following since the aquo complex has a lower extinction coefficient than the nitrato, the density would drop first and then eventually rise, and of course the two curves would come together eventually. 

Another interesting point is the relative rates of the reactions of the azido and thiocyanatopentaammines. The relative rates of these two reactants with iron (I I) ion are similar to those with chromium (I I), that is, the azide is four to five powers of ten more rapid than is the thiocyanato. I am suggesting that this might be a criterion for inner sphere activated complex as opposed to an outer sphere complex. With trisdipyridylchromium(II) ion, which must react via an outer sphere process, the azido and thiocyanato rates are relatively comparable, and the same also for vanadium (I I) ion which also probably procedes via an outer sphere activated complex. 

Chloro, 3-bromo, 3-iodo, and 3-nitro derivatives of 5,7-dimethyl-pyrazolo[l,5-a]pyrimidine derivatives were prepared by chlorination, bromination, iodination, and nitration of 3-unsubstituted 5,7-dimethyl-pyrazolo[l,5-a]pyrimidines. Reaction with bromine and potassium thiocyanate gave a 3-thiocyanato derivative, which was converted into the mercapto derivative upon saponification. Nitrosation gives the 3-nitroso derivative and acylation with trifluoroacetic anhydride affords the trifluoroacetyl derivative (74JMC645 77JMC386). 

The first sesquiterpene thiocyanate to be isolated from a marine sponge was (15, 45, 65, 7/ )-4-thiocyanato-9-cadinene (253) from Trachyopsis aplysinoides. The structures of this compound and of an isothiocyanate with a new carbon skeleton (254), were determined by X-ray analysis and two additional isothiocyanates (255-256) were identified [258]. Isothiocyanate 254 was synthesised using an oxidative radical cyclisation reaction as a key step [259]. 

The products of reduction of Fe(NCS)2+ by Cr2+ in aqueous solution containing thiocyanate ions (equation 36), include the isomers of [Cr(NCS)(SCN)(H20)4]+, which contains both bland S-bonded thiocyanate ligands.641 These isomers undergo spontaneous decomposition by parallel aquation (loss of the S-thiocyanato ligand) and isomerization (Cr—SCN— Cr—NCS) reactions. Details of the solution visible spectra of these isomers as well as those of similar chromium(III) complexes for comparison are listed in Table 68. From the compiled data it is apparent that the S-bonded thiocyanate ligand lies very close to Br- in the spectrochemical series while the N-bonded form lies between Nj and NO. 

Synthesis of copper and zinc complexes of 5,7-dimethyl-l,2,4-triazolo [l,5-a]pyrimidine has been reported [93AX(C)1902 94AX(C)510], Reaction of copper(II) thiocyanate with 5,7-dimethyl-l,2,4-triazolo[l,5-a]-pyrimidine (l) gave three different complexes two isomers of [Cu(NCS)2L2]2 and Cu(NCS)2L2 H20 (84IC2803). The mononuclear complexes, bis(thiocyanato-N)bis(6-methyl-l,2,4-triazolo[l,5-a]pyrimidine-jV-3)copper(II) and the polynuclear pseudo-layered complexes, bis(thio-cyanato-A0bis(5-methyl-l,2,4-triazolo[l,5-a]pyrimidine-A -3)copper(II) were prepared (89POL2313). 

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