2- benzothiazolines preparation

Oxoalkyl)benzothiazolines (prepared by the reaction of 3-methyl-2-phenylbenzothiazolim fluorosulfate with lithium enolates of ketones) act as enolate-transferring reagents in Lewis acid promoted cross aldol reactions of aldehydes with ketones (Equation (96)) <90BCJ497>. 

Over the years, many spiropyran structures have been prepared. The pyran component consists of benzopyran or naphthopyran and the heterocyclic part consists of indoline, benzothiazoline, benzoxazoline, benzoselen-azoline, phenanthridine, acridine, quinoline, benzopyran, naphthopyran, xanthene, benzodithiole, benzoxathiole, and saturated heterocyclic rings such as pyrolidine and thiazolidine. 

Methods available before 1971 for the preparation of thiol esters are briefly summarized in a review article.4 Since then, several newer techniques have been developed, to meet a certain set of criteria required for recent synthetic operations. This development may be summarized as follows. Whenever an acid chloride is available, the reaction of the T1(I) salt of a thiolate of virtually any kind, including alkane-, benzene-, 2-benzothiazoline-, and 2-pyridinethiol, proceeds efficiently and near-quan-titatively. However, if selective thiol ester formation in the presence of hydroxy or other functional groups in the same molecule is required, three main procedures are available. First, reaction of an acid (1), with... 

Benzothiazolines 72 are prepared by means of gallium(III) triflate mediated condensation of 2-aminobenzenethiol with fluorinated ketones followed by cyclization <07OL179>. Gallium triflate is a stable, water tolerant, recoverable, reusable, and environmentally friendly Lewis acid. Even when used in catalytic amounts, gallium triflate provides sufficient acidity required for the synthesis of fluorinated benzothiazolines. 

The pyrolysis of a number of benzothiazolines, which were prepared by the reaction of o-aminobenzenethiols with ketones, have been investigated by Elderfield and McClenachan . The first-order rate coefficients were estimated by measure-... 

A number of anionic Tl1" complexes containing terdentate ligands have been prepared.582 Examples are R2T1L, where R = Me or Ph, L = Aat or Sat [the compounds H2Aat and H2Sat being 4-(2-benzothiazolinyl)-2-penta-none and 2-(o-hydroxyphenyl)benzothiazoline, respectively]. The idealized structure of the Aat2 complex is (80). 

Benzothiazoline-2-thiones (CI 11) and their derivatives can be prepared from o-amino thiophenols and carbon disulfide (method A) 166,221,282). On the industrial scale, these compounds, which are important vulcanization accelerators, are prepared from anilines, sulfur and carbon disulfide under pressure and at high temperature (200° C) (method B). In spite of many attempts, the mechanism of this reaction has not been established. Sebrell and Boord 211 mention the following plausible mechanisms ... 

According to Teppema and Sebrell [357], the preparation of benzo-thiazoline-2-thiones from aryl amines, sulfur and carbon disulfide is not generally applicable. This has been confirmed by several other authors. Another synthesis, method C, has been worked out starting with o-nitro chloro benzenes. On warming these products in a solution of sodium hydrogen sulfide with slow addition of hydrogen sulfide in the presence of carbon disulfide, near 90% yields of benzothiazoline-2-thiones are obtained. 

The preparation of benzothiazoline-2-thiones from o-halo or w-halo anilines and carbon disulfide in basic medium is discussed at greater lenght in Section IV.4. 

This type of tautomerism is principally important for the preparation of chelates with five-membered metallacycles of composition MN2S2 from benzothiazoline-ligating compounds (Equation (16)). Ring-chain... 

A number of early reports on thiazolin-2-ylidene and benzothiazolin-2-ylidene have appeared and spectroscopic studies carried out. " " These were prepared either from preformed heterocyclic rings or from the... 

A direct synthesis of quaternary salts (e.g. alkylsulfates, iodides, bromides, perchlorates) of benzothiazole from 2-aminobenzenethiol has been narrated in Uteratue by Kiptrianov and Pazenko. Fry and Kendall synthesized quaternary salts of 2-alkylsulfanylbenzothiazole and used them in the synthesis of thiacyanine dyes (Fry Kendall 1951). Similar type of synthesis of 2-haloalkylsufanyl benzothiazolium salts was carried out by Knott in 1955 (Knott 1955). Brooker (1951) prepared benzothiazolium salts from substituted benzothiazoline and p-toluensulfonate for further conversion to cyanine dyes (Brooker et al 1951). 

ABSOLUTES. Entirely alcohol-soluble extracts prepared by alcohol extraction of concretes or related fat-soluble or waxy materials, alcohol-insoluble substances being removed before evaporation of the solvent ABTS. 2,2 -Azino-bis-(3-ethyl-1,2-dihydro-benzothiazoline 6-sulfonate)... 

Type C Syntheses (N—C6H4—S—C).—Conversion of o-nitroarylthio-acetic acids, prepared from a-mercaptoacetic acid and the appropriate derivative of < -nitro-chlorobenzene, into the corresponding benzothiazolin-2-one (9) can be brought about by treatment with acetic anhydride followed by hydrolysis with base or acid" (see Vol. 3, p. 622). 

Benzothiazolines and Benzothiazolln>2 ones - Synthesis, A series of benzothiazolin-2-ones (215 R -R =H,Me,MeO,Cl,F,R =R =H) have been prepared by AC2O cyclisation of arylthioacetic acids and subsequent deacetylation of the concomitant 3-acetyl pro-ducts. U-Chloro-3-inethylbenzothiazolin-2-one (215 R -R =H, R =Cl,R =Me) results from AlCl cyclisation of 2-ClCgHj N(Me)-C(0)SC1 the latter is formed from 2-ClCgH2jNHMe and C1C(0)SC1 in PhNMe2/toluene ,... 

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