Benzothiazoles 2-lithio

Benzothiazole, 2-ethoxycarbonyl-6-hydroxy-synthesis, 6, 325 Benzothiazole, 2-ethyl-reactions, 6, 276 Benzothiazole, hexahydro-synthesis, 5, 120 Benzothiazole, 2-hydroxy-reactions, 6, 285 synthesis, 6, 322, 324 Benzothiazole, 2-(o-hydroxyphenyl)-structure, 6, 238 Benzothiazole, 2-lithio-... 

Benzothiazole, 2-amino-4,5,6,7-tetrahydro-7-imino-4,4,5,5,6,6-hexafluoro-, 60, 23 Benzothiazole, 2-chloro-, 59, 276 Benzothiazole, 2-fluoro-, 59, 277 Benzothiazoles, 2-guanidino-, formation by rearrangement, 56, 111 Benzothiazole, 2-lithio-, use... 

In an interesting study with potential for the synthesis of 3-substituted pyridines, Katritzky has shown that LDA metalation of the benzothiazol-2-yl thioether 479 gives the highly coordinated lithio species 480, as demonstrated by quench with several electrophiles to give products 481 (Scheme 144) [87H(26)427]. 

Thiazole and benzothiazole exchange the C-2 hydrogen for lithium or magnesium when treated with an ethereal solution of phenyl- or butyl-lithium at -60 °C or ethylmagnesium bromide at 0 °C then at 25 °C (Scheme 31). When the 2-position of thiazole is occupied by a methyl group, the reaction of butyl-lithium at low temperature (-100 °C) affords three independent lithio salts (54, 55 and 56 Scheme 32) in the approximate ratio 52 3 45. As the temperature is increased, the 2-lithiomethyl derivative (54), which is less stable than the 5-lithio isomer (56), decomposes up to +5 °C at which point it has almost entirely disappeared. 

Related Reagents. Benzothiazole Carbon Monoxide A, A -Diethylaminoacetonitrile iVJV-Dimethyldithiocarbamo-ylacetonitrile 2-Lithio-l,3-dithiane Methylthiomethyl p-Tolyl Sulfone 2- Trimethylsilyl)thiazole. 

The vinylbenzothiazoles can also function as very efficient Michael acceptors (78TL13). The a-lithio derivative of acetone dimethylhydrazone undergoes clean conjugate addition to the vinylbenzothiazole derived from cyclohexanone to provide, upon quenching the a-lithiobenzothiazole anion with methyl iodide and hydrolyzing the dimethylhydrazone group, the ketone (579) (93% overall, 86 14 cis trans). The pure cis keto benzothiazole was converted to the cis keto aldehyde (580), and then cyclized with p-toluenesulfonic acid to the A -3-octalone (581 Scheme 127). Many other examples of the use of this chemistry for the construction of fused and spiro ring systems have been developed. 

Baudin, J. B., Hareau, G., Julia, S. A., Ruel, O. A direct synthesis of olefins by the reaction of carbonyl compounds with lithio derivatives of 2-[alkyl- or 2 -alkenyl- or benzylsulfonyl]benzothiazoles. Tetrahedron Lett. 1991, 32,1175-1178. 

Benzothiazoles and benzimidazoles (blocked or protected on nitrogen) lithiate at the hetero-ring 2-position. This allows subsequent reaction with the usual range of electrophiles the examples below show the introduction of iodine and a silicon substituent 2-lithio-benzimidazoles also react efficiently with simple esters to give ketones. ... 

Da das gebildete 2-Lithio-l,3-benzothiazol durchweg ohne Isolierung weiter umgesetzt wird, werden Arbeitsvorschriften an entsprechender Stelle angegeben. 

Lithio-l,3-benzothiazol-3-oxid (Herstellung s. u.) laBt sich mit Kohlendioxid (als Trockeneis) in 2-Carboxy-l,3-benzothiazol-3-oxid iiberfiihren321 ... 

Lithio-l,3-benzothiazolreagiert mit Kohlensaure-chlorid-dimethylamid zu 2-Dimethylamino-carbonyl-1,3-benzothiazol, das mit iiberschiissiger Lithium-Verbindung Bis-[1,3-benzothiazol-2-yl]-keton ergibt403. 

Zur Reaktion von 2-Lithio-l,3-benzothiazol mit Organo-isothiocyanatcn zu 2-(Organoami-no-thiocarbonyl)-l, 3-benzothiazolen s.Lit.406. 

Metallo-l,3-benzothiazole ergeben mit Carbonsaure-Derivaten 2-Acyl-1,3-ben zot hi azole. So erhalt man aus l-Lithio-l,3-benzothiazol (1,1 Aquivalente) mit Bcnzoesaure-ethylester bzw. Benzonitril 76 bzw. 82% 2-Benzoyl-l, 3-benzothiazol 07 ... 

Lithio-l,3-benzothiazol ergibt mit Chlor-trifluor-ethen 14% 2-(2-Clibr-1,2-difluor-ethenyl)-l,3-benzothiazol [Schmp. 93-95° Sdp. 82-84°/0,5 Torr (67 Pa)]416 ... 

Lithio-l,3-benzothiazol reagiert mit Aldehyden und Ketonen in guten Ausbeuten zu 2-(l-Hydroxy-alkyl)-1,3-benzothiazolen403,417,418. Ergebnisse sind in Tab. 94 (S. 956)zusam-mengestellt. 

Tab. 94 2-(l-Hydroxy-alkyl)-l,3-benzothiazole aus 2-Lithio-l,3-benzothiazol und Carbonyl-Verbindungen... 

Die Reaktion von 2-Trimethylsilyl-l,3-benzothiazol mit 3-Oxo-cyclohexen in Gegenwart von Casiumfluorid verlauft, im Gegensatz zur Umsetzung von 2-Lithio-l,3-benzothiazol mit a,/i-ungesiittigten Carbonyl-Verbindungen (s.S. 956, dort Tab. 94), offenbar als 1,4-Addition man erhalt 50% 2-(3-Oxo-cyclohexyl)-l,3-benzothiazolA1° (zur Arbeitsweise s.S. 954) ... 

Lithio-1,3-benzothiazol ergibt bei der Umsetzung mit 1-Azido-l-phenyl-ethen (— 78°) und nachfolgender saurer Aufarbeitung 53% 2-Amino-1,3-benzothiazoliS0-. 

Lithio-l,3-benzothiazol laBt sich mit Chlor-trimethyl-silan in 2-Trimethylsilyl-1,3-benzothiazol (77%) iiberfuhren403,404 (Arbeitsvorschrift s. S.953) ... 

Zur Synthese von 2-Triorganostannyl-l,3-benzothiazolen aus 2-Lithio-l,3-benzothiazol und Chlor-triorgano-stannanen s.Lit.451 ... 

Metalated thiazoles are only stable at low temperatures. The formation of an isonitrile in the procedure below clearly shows this poor stability (compare Ref. [189]). On the other hand the methylthio derivative of benzothiazole is formed in good yield upon addition of a methythiolation reagent to the solution resulting from the interaction between benzothiazole and sodamide in liquid ammonia. This situation may be analogous to the ambident behaviour of 2-lithio-4,5-diphenyl-oxazole [193]. 

Spiroannelation, Cyclic ketones readily condense with the a-lithio derivative of 1 giving a,)3-unsaturated benzothiazoles (j8,) -disubstituted enal equivalents). These in turn may be converted into spiro derivatives as shown in equation (I). ... 

Similarly, MyllymSki et al. have employed this concept in the synthesis of aryl ketones via the reaction of the lithio benzothiazole with an aryl acid chloride to produce the desired ketone. A series of such carbonyl compounds was synthesized and evaluated as potential fatty acid amide hydrolase (FAAH) inhibitors. 

Other metalated compounds such as silanes and stannanes can be derivatized likewise. For example, the corresponding stannanes of lithio benzothiazole can also be synthesized with relative ease by treating the lithiated species with organotin chlorides. 

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