Benzothiazoles aldehydes

The roasted root contains a steam-distillable fraction (aroma), which is composed of pyra-zines, benzothiazoles, aldehydes, aromatic hydrocarbons, furans, phenols, organic acids, and others, totaling 3 3 identifiedcompounds, among which acetophenone is a characteristic component of roasted chicory not previously reported as a component of aroma of any heated food products such as coffee. Other constituents of the roasted root include 2-acetylpyrrole, furfural, phenylacetaldehyde, phenylacetic acid, and vanillin. Small amounts oftwo indole alkaloids ((3-carbolines), barman and norharman, have also been isolated from the roasted root. ... 

There are several new methodologies based on the Julia olefination reaction. For example, 2-(benzo[t/Jthiazol-2-ylsulfonyl)-j -methoxy-i -methylacetamide 178, prepared in two steps from 2-chloro-iV-methoxy-jV-methylacetamide, reacts with a variety of aldehydes in the presence of sodium hydride to furnish the ajl-unsaturated Weinreb amides 179 <06EJOC2851>. An efficient synthesis of fluorinated olefins 182 features the Julia olefination of aldehydes or ketones with a-fluoro l,3-benzothiazol-2-yl sulfones 181, readily available from l,3-benzothiazol-2-yl sulfones 180 via electrophilic fluorination <06OL1553>. A similar strategy has been applied to the synthesis of a-fluoro acrylates 185 <06OL4457>. 

In soft cheeses, such as Brie, Camembert, and Limburger, the following sulfur compounds were implicated 3-(methylthio)propanol, MT, DMS, DMDS, DMTS, dimethyl tetrasulfide, methyl ethyl disulfide, diethyl disulfide, 2,4-dithiapentane, 3-methylthio-2,4-dithiapentane, methional, 2,4,5-trithiahex-ane, 1,1-fe-methylmercaptodisulfide, methyl thioacetate (=methanethiol acetate), benzothiazole, methylthiobenzothiazole, methyl ethyl sulfonate, methyl methane thiosulfonate, thiophene 2-aldehyde, and H2S.34 Many of these were only present in small amounts Limburger cheese was notable for 13.2% of DMDS, 0.5% of methyl thioacetate, and 0.8% of DMTS. 

One of the reasons that the 2-lithiobenzothiazole system has received attention is the ability of the benzothiazole group to act as a synthon for an aldehyde or ketone group (78TL5 85H295 88BCJ3637). Thus, after reaction of the anion with an electrophile, the product is alkylated with methyl iodide followed by the nucleophilic addition of either an alkyl group or a hydride ion. Subsequent hydrolysis results in the formation of a ketone or an aldehyde (Scheme 100). 

In the case of the benzothiazole system, both aldehydes and mixed ketones have been synthesized by reduction or alkylation of the appropriate carbonyl precursors. The carbonyl compounds are in turn prepared from the benzothiazole-2-anion either directly by reaction with esters or indirectly by reaction with aldehydes followed by PCC oxidation (Scheme 154) (85H2467 91BCJ3256). 

Benzothiazoles have been prepared by oxidative condensation of aldehydes with resin-bound 4-mercapto-3-aminobenzoic acid derivatives (Entry 8, Table 15.18), and by dehydration of 2-mercaptoanilides (Entry 9, Table 15.18). Oxidation of 2,3-di-hydrobenzothiazoles to benzothiazoles can occur spontaneously, without the need of any additional oxidant [231]. Polystyrene-bound 4-iodobenzoate reacts with thiazole in the presence of Pd(0) to yield a 4-(4-thiazoIyl)benzoate (Entry 10, Table 15.18). If Cul is added to the reaction mixture, however, the 4-(2-thiazolyl)benzoate results [141]. 

Both 2-(p-tolyl)-5-phenylthiazole and 2-(p-tolyl)benzothiazole can be converted to the corresponding stilbene derivatives (see Table IX) by reaction with aromatic aldehyde anils under the influence of potassium hydroxide.11 Also, 2,5-bis(p-tolyl)thiazolo[5,4 /]thiazole (118) yields,... 

The synthesis of cyclopropyl compounds containing the olefin replacement for the amide bond but without the additional primary chiral amino substituent were prepared by modified Julia olefination procedures. Addition of the benzothiazole sulfone 44 to aldehyde 39 gave trityl protected olefins in a 1 1 ratio. These... 

The Modified Julia Olefination (or Julia-Kocienski Olefmation) enables the preparation of alkenes from benzothiazol-2-yl sulfones and aldehydes in a single step ... 

Benzothiazole is acylated selectively in the 2-position by acyl radicals generated from a variety of aldehydes under the influence of the redox system f-butylhydroperoxide-ferrous sulfate. The nucleophilicity of acyl radicals is confirmed by the higher reactivity of 6-nitrobenzothiazole. The reaction, which could detect acyl radicals in the oxidation of aldehydes by various oxidizing agents, could serve as a diagnostic test for the presence of such radicals (71JCS(C)1747). 

Another important way in which to achieve reaction with electrophiles is to utilize silyl derivatives (prepared in turn via metallation chemistry). Thus, for example, 2-silyl-thiazoles and -benzothiazoles react readily with esters <2001JME1286>, ketones <2005JOC8556>, and aldehydes <2001T4729>, all facilitated by fluoride from TBAF. Acid chlorides <2004JOC8903> do not require fluoride assistance. 

It is well known that addition of benzothiazole to dimethyl acetylenedicarboxylate (DMAD) leads to the formation of zwitterion 115. This intermediate can be trapped with various aryl aldehydes, according to a recent study <07TL4391>. Thus, heating a solution of benzothiazole, DMAD and aryl aldehyde 116 in toluene generates oxazinobenzothiazole 117 as a single isomer in moderate yield. 

The modified Julia-Lythgoe alkenation known as Julia-Kocienski alkenation is one-step synthesis of alkenes from benzothiazol-2-yl sulfones (RCH2SO2BT) 4.59 and aldehydes, which is an alternative procedure that leads to the alkene in one step and offers very good -selectivity. 

The reaction pathway greatly alters when benzothiazole sulfone 4.59 is used instead of phenyl sulfone. The initial addition of the sulfonyl anion 4.60 to the aldehyde is reversible and gives alkoxide intermediates 4.61 and 4.62 (Scheme 4.37). Whether the anti- or... 

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