Thiazin 2-vinyl

In a similar manner, 2,2,4-trimethyl-27/,677-pyrimido[2,T4][l,3]thiazines with 7-formyl, 7-acetyl, or 7-C02Me substituents were obtained in good to excellent yields by reacting Ar,Ar-dimethyl-Ar -(4,6,6-trimethyl-6//-l,3-thia-zin-2-yl)formamidine with acrolein, methyl vinyl ketone, or methyl acrylate, respectively <2002S403>. 

Conjugate addition of methylamine to vinyl alkynyl sulfoxides and sulfones also led to formation of 1,4-thiazine 1-oxides and 1,1-dioxides (Equation 74) <1979S47>. 

The chemistry of the 2-vinyl-l,3-thiazetidines 98 is interesting because these compounds undergo rearrangement to the thiazolidines 99 on catalytic hydrogenation and rearrangement to the thiazines 100 on treatment with Wilkinson s catalyst (Scheme 29) <1999J(P1)3569>. 

Moreover, the 2-vinyl-l,3-thiazetidine 98a (R1 = R2 = Et) undergoes rearrangement to thiazine sulfone 101 when treated with peracid. A by-product sultine compound 102 was isolated in 6% yield from this reaction. This could be the result of a [2,3]-sigmatropic rearrangement of the sulfone. The reduced 2-vinyl-l,3-thiazetidine 103 is also oxidized with peracid affording the thiazine sulfone 104 but no product corresponding to the sultine was detected (Scheme 30) <1999J(P1)3569>. 

Vinyl-1,3-thiazetidines have been prepared by novel, high-yielding photochemical rearrangements of the corresponding 1,3-thiazines (Equation 22) <1999J(P1)3569>. 

There is very little information on the NMR spectral properties of 5,6-dihydro-2//-l,4-thiazines. The vinylic proton of 87 absorbs at S 8.04 and it displays long-range coupling (J = 2.3 Hz) with the 4-proton. ... 

With the development of the application of MBH adducts in the synthesis of cyclic products, other heteroatoms such as an S-atom have also been introduced into cyclic products. As by-product of a MBH reaction, 3-(a-hydroxybenzyl)thiochromanone 827 and 3-(a-hydroxybenzyl)selenochro-manone 828 were obtained, respectively, in the chalcogeno MBH reaction of 2-(methylchalcogeno)phenyl vinyl ketones with aldehydes (Scheme 4.239). " More recently, MBH bromides 829 have been treated with thiourea in the presence of a base such as NaHCOs to furnish 1,3-thiazin-4-ones 830 in 75-91% yields (Scheme 4.240). ... 

Reactions.—2-Iminocyclopentanedithiocarboxylic acid adds to Schiff bases at room temperature to form esters (130) these cyclize to 1,3-thiazines (131), with loss of arylamine, on warming. Similar 1,3-thiazines are readily obtained from cyclohexanone, CSj, and ammonia. The addition of dithio-acids to dienes goes by a concerted reaction at 50 C and by a free-radical mechanism at higher temperatures, the products being allyl or vinyl dithioesters and/or dithiolans, e.g. 

Phenothiazines are well known redox systems and poly(2-vinyl phenothiazine) (IV) is readily oxidized "by agents like ferric chloride or bromine and by oxygen in presence of light. Shigehara and COworkers synthesized the acrylamide derivatives of the thiazine dyes (v), Thionin and Azure B, and copolymerized them with N vinyl pyrrolidone by free radical methods to give wa ter soluble polymeric dyes. ... 

Since cystamine is one of the most effective radiation prophylactics known, the preparation and polymerization of S-vinyl-N-vinylthio-carbamates (37) (XXI) was utilized in an attempt to prepare alternating poly(vinylamine-vinylmercaptan)copolymers (Scheme III). The divinyl monomers were prepared by dehydrochlorination of the respective S-2-dhloroethyl-N-2-chloroethylthiocarbamates (XX). Polymerization of these monomers under a variety of conditions yielded terpolymers (XXII) composed of the tetrahydro-l,3-thiazin-2-one moiety as well as poly-S-vinyl and poly-N-vinyl units. Attempts to isolate polymeric a-amino y-thiols (XXIII) formed by hydrolysis of the resultant terpolymers (XXII) proved unsuccessful. 

The carbonylation of allylic phosphates followed by elimination may form a vinylic ketene intermediate, which may further undergo [2+2]-cycloaddition with 2-aryl-1,3-thiazines to afford bicyclic /3-lactams highly diastereoselectively (eq 8). ... 

Several new examples of the reactivity of thioamides towards compounds containing activated carbon-carbon double or triple bonds have appeared. Thus little-known thiazine derivatives have been synthesized by treatment of primary thioamides with a -unsaturated ketones pyridine-2-thiones afforded, on treatment wi a-bromo-a 3-unsaturated acids or acetylenedicarboxylic acid, dihydrothiazolo[3,2-a]pyridinium salts, whereas die vinyl sulphides (263) were the products obtained in their reactions with propiolic or phenylpropiolic acid a Diels-Alder adduct was produced by the reaction of the thioamide (264) with dimethyl acetylenedicarboxylate. NN -Disubstituted phenylpropiolamidines (265),... 

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