2H,l,4-benzothiazines

Napolitano, A. Di Donato, R Prota, G. Zinc-Catalyzed Oxidation of 5-S-Cystei-nyldopa to 2,2 -Bi(2H-l,4-benzothiazine) Tracking the Biosynthetic Pathway of Trichochromes, the Characteristic Pigments of Red Hair. J. Org. Chem. 2001, 66, 6958-6966. 

In einer ahnlichen, phosphorsaure-katalysierten, intramolekularen Cycloaddition entste-hen 3,3-Dimethyl-3,4-dihydro-2H-l,4-benzothiazine aus 2-(2-Methyl-allylthio)-anilinen in guten Ausbeuten3 ... 

Fujita, M., Ito, S., Ota, A., Kato, N., Yamamoto, K., Kawashima, Y, Yamauchi, H., and Iwao, J. 1990. Synthesis and calcium ion antagonistic activity of 2-[2-[(aminoaIkyl)oxy]-5-methoxyphenyl]-3,4-dihydro-4-methyl-3-oxo-2H-l,4-benzothiazines. Journal of Medicinal Chemistry, 33 1898-1905. 

H-l,4-Benzothiazine 2-(Carboxy-methyl)-3-oxo-3,4-di hydro- E9a, 455f. (2-SH — anilin + Malein-saure), 460 (2-SH —anilin + 2-Br-butandisiiure) 2,1-Benzothiazol 3-Methoxy-7-methoxycarbonyl- E8a, 870 (Oxa - Thia)... 

A full spectral characteristics including /cp couplings has been reported by Schmutzler and co-workersfor ( )-2,2-diethyl-3,4-dihydro-2/f-l,4-ben-zothiazin-3-yl dimethylphosphine oxide and ( )-2,2-diethyl-3,4-dihydro-2H-l,4-benzothiazin-3-yl dimethylphosphine sulfide. 

With more powerful oxidizing agents, such as chloranil, benzothiazines can be converted to the dehydro dimers A2 2 -bis-(2H-l,4-benzothiazines)(157 and 158). These isomeric species interconvert readily even at ambient temperatures.36 The structures were confirmed by X-ray analysis, and the cis isomer is shown to predominate at room temperature. 

Subsequently, it was discovered that even exposure to air was sufficient to convert the parent compound, 2//-l,4-benzothiazine 8, to the trans dimer 159, a yellow-orange solid. Solutions of this isomer are photochromic, 159 interconverting readily with the cis isomer 160 on exposure to sunlight.36 Such photochromism had already been observed with related natural pigments based on the A2,2 -bi-(2H-l,4-benzothiazine) system.171... 

C hlor-2-oxo-2H-l,4-benzothiazine ergeben mit Natriumcarbonat in Alkoholen 2-Alkoxy-carbonyl-1,3-benzothiazole324 z.B. ... 

N-Substituted 2H-l,4-benzothiazin-3(4 -one derivatives 57 undergo selective and efficient anodic fluorination in EtjN-SHF/MeCN to give the corresponding fluorinated products in good yields (Eq. 110). In these cases, fluorination does not take place on the benzene ring. When R in 57 is hydrogen, only polymerized products are formed. 

Azaphenothiazines 117 (80TL421, 83JMC845) have been synthesized via thermal cyclization from 2H-l,4-benzothiazine-3(4H)-thione 111 (69JMC290). The intermediate was a cyanoacetamide adduct 113 that has been converted into dimethylami-noethylene 115 and then in the monoaminoethylene amide 116 (Scheme 53). 

As yet the stereochemistry of the A > -bi-(benzothiazine) skeleton in the trichosiderins and in (93) and (94) has not been defined, although indirect evidence indicates that the isolated products may well be an equilibrium mixture of both geometrical isomers. Support for this view derives also from a recent study on the stereochemistry of some A -bi-(2/T-l,4-benzothiazine) derivatives (96), which have been obtained in good yield by oxidation of the corresponding 2H-l,4-benzothiazines (95) with chloranil... 

Li H, Dryhurst G. Irreversible inhibition of mitochondrial complex I by 7-(2-aminoethyl)-3,4-dihydro-5-hydroxy-2H-l,4-benzothiazine-3-carboxylic acid (DHBT-1) a putative nigral endotoxin of relevance to Parkinson s disease. J Neurochem 1997 69 1530-1541. 

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