Pyridine-2-thione, reaction with

Imidazo[4,5-c]pyridine-2(3f7)-thione, 1-methyl-reactions with acrylonitrile, 5, 620 Imidazo[l,2-a]pyridine-2(3H)-thiones synthesis, 5, 632... 

The ring expansion reaction of diaryl cyclopropenones and cyclopropene thiones occurring with pyridinium, sulfonium, and phosphonium enolate betaine 427268-270) is related to 1,3-dipolar cycloadditions. This process results in formation of 2-pyrones 428 by loss of pyridine (or sulfide or phosphine) and insertion of the remaining fragment C=C-0 to the C1(2)/C3 bond of the cyclopropenone ... 

Heating compound 299 with phosphorus pentasulfide in a mixture of dioxane and pyridine gave 7-(2,3,5-tri-0-benzoyI-/3-D-ribofuranosyl) thieno[3,4-d]pyrimidin-4(3//)-thione 374, in 49% yield. Thione 375, obtained by debenzoylating compound 374, was converted into the 4-methyl-thio-7-/3-D-ribofuranosylthieno[3,4-d]pyrimidine 376 by reaction with excess methyl iodide in 0.1 N aqueous sodium hydroxide. Substitution of the... 

Azine approach. Fused 1,2,3-thiadiazoles are often conveniently prepared from vicinal aminomercaptoarenes by a diazotization reaction the mercapto group adds to the initially formed diazonium group to form the ring. So far this reaction has not been reported in this series, but a mechanistically similar reaction results when l,4-dihydro-7H-t>-triazolo[4,5-h]pyridine-7-thione (655 R = H) is heated in ethanol to furnish the 1,2,3-thiadiazole (657). Heating the latter under alkaline conditions reverses the reaction with... 

Synthesis of thiazolo[3,2-a]pyridin-3(2//)-one can also be accomplished by an alternate route in which a thiazole ring is built onto a pyridine ring. Thus, copper-catalyzed reaction of piperidine-2-thione (95) with methyl diazoacetate affords 5,6-dihydro-7//-thiazolo[3,2-a]pyridin-3(2//)-one 97) (80LAI68) (Scheme 22). During the reaction uncyclized intermediate (96) could not be isolated, it evidently cyclized immediately to the bicyclic product (97), whereas with the pyrrolidine-2-thione the corresponding uncyclized product was isolated (80LAI68) (Scheme 22). 

Dehuri and Nayak (83JIC970) reported that 3,4,5,6,7,8-hexahydro-l,3-diazocine-2-thione (213), obtained from 1,5-dibromopentane and thiourea in boiling ethanol, reacts with chloroacetic acid or its ethyl ester followed by basification to give 5//-6,7,8,9-tetrahydrothiazolo[3,2-a]-[ 1,3]diazocin-3(2//)-one (214). The reaction of 213 with ethyl chloroacetate was not smooth and the yield was low. The thione 213, on reaction with ethyl chloroacetate and aromatic aldehydes in the presence of pyridine and piperidine, furnishes the arylidene product 215 which is also obtained from 214 and aromatic aldehydes. No spectral data are cited to confirm the thiazolidinone structures 214 and 215 (Scheme 50). 

Reaction of 3//-imidazo[4,5-y]quinoline-2-thione (404) with chloroacetic acid gives acid 405 which, on treatment with a mixture of acetic anhydride and pyridine, undergoes cyclization to furnish a product confirmed by the appearance of a band at 1735 cm (N—C=0) and molecular ion peak [M] at m/z 241. Thiazolo[2, 3 2,3]imidazo[4,5-y]quinolin-6(7//)-one (406), in preference to the other possible isomer thiazolo[3, 2 l,2]-imidazo[4,5-y]quinolin-8(7//)-one (409), was assigned to the cyclized product on the basis of the comparative studies of proton signals of the cyclized product (406 or 409) with those of 407 or 408 (obtained by the reaction of 404 and 1,2-dibromoethane), as well as with the proton signals of acid 405 [86IJC(B)264] (Scheme 93). 

The level of substitution of the antibody after reaction with SPDP is determined spectrophotometrically. A sample the derivatized antibody is treated with DTT at a final concentration of 5 mM, and the optical density measured at 280 nm and 343 nm. The pyridine-2-thione released by reduction has a molar extinction coefficient at 343 nm of 8.08 X 10 Af" cm (12). This product also absorbs at 280 nm with a molar extinction coefficient of 5.1 x 10 Af" cm . The true protein absorbance is determined from the formula ... 

As indicated previously (Ref. 2 p. 188), if a 3- or 4-aryl-l,2-dithiolium ion is treated with a methyl acyldithioacetate in pyridine, the reaction takes a different course and gives a 3-acylthiopyran-2-thione. Cyanothioacet-amide and ethyl cyanoacetate react in a similar fashion. These reactions are summarized in Scheme 24. 

Reaction of l-methylimidazo[4,5-c]pyridine-2(3//)-thione (177) with nitric acid, or that of l-methylimidazo[4,5-c]pyridine and its 2-methyl derivative with a mixture of nitrous... 

---