Thiazinic reaction

Adducts from various quaternary salts have been isolated, in reactions with aldehydes, a-ketoaldehydes, dialkylacylphosphonates and dialkyl-phosphonates, isocyanates, isothiocyanates, and so forth (Scheme 15) (36). The ylid (11) resulting from removal of a Cj proton from 3.4-dimethyl-S-p-hydroxyethylthiazolium iodide by NEtj in DMF gives with phenylisothiocyanate the stable dipolar adduct (12) that has been identified by its NMR spectrum and reactional product, such as acid addition and thiazolidine obtention via NaBH4 reduction (Scheme 16) (35). It must be mentioned that the adduct issued from di-p-tolylcarbodiimide is separated in its halohydrogenated form. An alkaline treatment occasions an easy ring expansion into a 1,4-thiazine derivative (Scheme 17) (35). 

But when the reaction is carried out in an aqueous solution of sodium hydrogen carbonate, extension of the ring occurs with formation of dihydro-l,4-thiazine derivative (Scheme 19). the structure of which has been established by mean of NMR and infrared spectra (41). 

Takamizawa et al. developed a general ring-expansion reaction of heterocycles that, applied to thiazolium salts, yields 1,4-thiazines (496, 497) thiamine (220) reacts with dialkyl acylphosphonates (221) to give the tricyclic 1,4-thiazine (222) (498), which is easily hydrolyzed to dihydro-1,4-thiazinone (223) (499) (Scheme 106). In the case of thiazolium slats containing no functional groups (224), 1,4-thiazine derivatives (226) were directly obtained in fairly good yields (Scheme 107). 

Other ring-expansion reactions have already been mentioned in regard to addition reactions leading to pyrrolothiazoles (Section III. 3), which sometimes rearrange to 1,4-thiazines (333, 497). 

Photopolymerization reactions are widely used for printing and photoresist appHcations (55). Spectral sensitization of cationic polymerization has utilized electron transfer from heteroaromatics, ketones, or dyes to initiators like iodonium or sulfonium salts (60). However, sensitized free-radical polymerization has been the main technology of choice (55). Spectral sensitizers over the wavelength region 300—700 nm are effective. AcryUc monomer polymerization, for example, is sensitized by xanthene, thiazine, acridine, cyanine, and merocyanine dyes. The required free-radical formation via these dyes may be achieved by hydrogen atom-transfer, electron-transfer, or exciplex formation with other initiator components of the photopolymer system. 

The reaction of the cyanoquinoline (206) with CS2 to give (207) involves a 4-amino-1,3-thiazine intermediate similar to that encountered previously (Section 2.15.5.5.1) (67T891). 

In Corey and Chaykovsky s initial investigation, a cyclic ylide 79 was observed from the reaction of ethyl cinnamate with ylide 1 in addition to 32% of cyclopropane 53. In a similar fashion, an intermolecular cycloaddition between 2-acyl-3,3-bis(methylthio)acrylnitrile 80 and 1 furnished 1-methylthiabenzene 1-oxide 81. Similar cases are found in transformations of ynone 82 to 1-arylthiabenzene 1-oxide 83 and N-cyanoimidate 84 to adduct ylide 85, which was subsequently transformed to 1-methyl-lX -4-thiazin-l-oxide 86. ... 

Disubstituted derivatives of 4-mercaptoquinazolines were obtained in good yields by reaction of 5,6-benzo-l,3-thiazine-4-thione with amines (see 7b). 

A 3,4,8,9-tetrahydropyrido[2,l-c][l,4]thiazine 336 and a benzo(A)-l,4-thiazine 335 was isolated from the reaction mixture of enaminone 334 and 2-(3-chlorobenzylidene)acetylacetate (99T7915). Reactions of enamines 334 and 337 with DMAD in MeOH yielded addition products 338 and 339 and bi- and tricyclic derivatives 340 and 341, respectively. The latters could be obtained in quantitative yields when the addition products 338 and 339 were heated in refluxing MeOH. 

Amantadine is used cautiously in patients with seizure disorders, hepatic disease, psychosis, cardiac disease, and renal disease The antihistamines, pheno-thiazines, disopyramide, and alcohol increase the risk of adverse reactions when administered with amantadine... 

Similarly, the reaction of ammonia with an excess of 539 produces bis-[2-(l-oxotetrahydro-l,4-thiazin)-ethyl] sulphoxide 541632 (equation 340). 

Although the photodriven reactions of chromium carbene complexes with imines superficially resemble those of free ketenes, there are major differences. The optically active oxazolidine carbene (Table 5) gave excellent yields and high ee values when allowed to react with imidates, oxazines, thiazines, and... 

An asymmetric route to the 5,6-dehydro-4H-1,3-thiazine skeleton via an asymmetric /refero-Diels-Alder reaction [95]... 

Conjugate addition of azide ion to dihydropyran-2,5-diones affords the 3-amino derivative <96SL341>, whilst reaction with bisnucleophiles provides a route to piperazines, thiazines and diazepines <96JHC703>. 

A potential insecticide that is a derivative of tetrahydro-l,3-thiazine undergoes a number of reactions resulting in some 43 products of which the dimeric azo compound is the principal one in aqueous solutions (Figure 1.6) (Kleier et al. 1985). 

The majority of nonsteroidal antiinflammatory agents contain an acidic carboxyl group. A series of experimental agents in this class have been prepared in which the acidic proton is supplied by a highly enolizable proton from a function such as a p-dicarbonyl incorporated into a heterocyclic system. As an example, an acylated, highly oxidized isoquinoline moiety can fulfill this function (see also the benzo-thiazines below). Toward this end, reaction of... 

Thiazines, a heterocyclic system which is found, for example, in antibiotics of the cephalosporin type, were synthesized using a solvent-free domino procedure by Yadav and coworkers [24]. Hence, reaction of N-acylglycines 10-64, an aromatic... 

Phenyl-l,2,3,6-tetrahydropyrido[2,l- ][l,3]thiazino[3,2- ]quinolin-6-ones were prepared by the reaction of 2-mercapto-5-phenyl-l,4-dihydroquinolin-4-ones with 1,3-dihalopropane <1997JAK97/278780>. 7-Acetyl-2-aryl-9-cyano-6-methyl-8-phenyl-3,4-dihydro-277,877-pyrido[2,l- ][l,3]thiazin-4-ones were obtained from 5-acetyl-3-cyano-6-methyl-4-phenyl-l,2,3,4-tetrahydropyridine-2-thione with 3-aryl-2-propenoyl chloride <2002CHE761>. Reaction... 

Oxidation of 8-(l-methylethenyl)-2-oxo-7-thia-l-azabicyclo[4.3.0]octa-3,5-diene-5,8-dicarboxylate and its 3,4-dihydro derivative with peracids gave diethyl 3-methyl-6-oxo-2/7,6/7-pyrido[2,l- ][l,3]thiazine-4,9-dicarboxylate and its 7,8-dihy-dro derivative, respectively < 1999J(PI)3569>. Reaction of NH2(CH2)3NH2 with 5-O-methanesulfonyl-L-gulofuranose... 

Hydroxy-perhydropyrimido[2,Tr-][l,4]oxazine condensed into the pentacyclic compound 319 on heating in aqueous solution. The 9-OH-9-Me analogue did not undergo this reaction < 1996H(43) 1991 >. 7,8-Diamino-3,4-dihydro-277-pyrimido[2,1 -b [ 1,3]thiazin-6-one and 8,9-diamino-3,4-dihydro-2/7,6/7-pyrimido[6, -b][ 1,3]thiazin-6-one when reacted with benzamidine. HC1 in a melt at 220 °C in the presence of anhydrous NaOAc formed the purine derivatives 320 and 321, respectively <1996JME2529>. 

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