Jacobson-Hugershoff synthesis

Jacobson-Hugershoff Synthesis (Type B CgHs—N—C—S).—Examples of compounds prepared by this well-established method include (oxidizing agent in parentheses) the imine (4) (Bra in CHCla), the 2-substituted benzothiazoles [1 R = CH(CN)C(0)Ph] (potassium ferricyanide), and the benzothiazoles (1 R = NHa, NHPh, etc.) variously substituted in the benzene ring with methyl, bromo-, chloro-, or nitro-groups (plumbophosphates).  

Other Type B Syntheses.— The interaction of 2-picoline with 3-substituted anilines in the presence of sulphur under Willgerodt-Kindler conditions, reported 

Ethyl 2-bromocyclohexanone-6-carboxylate condenses with aromatic thio-anilides in the presence of base to give compounds (7), which are readily dehydrated to 4,5,6,7-tetrahydrobenzothiazoles. Compounds with Ar = NHAr may be prepared similarly.  

3-Amino-l,2-dithiolium salts (8 R = aryl, R = aryl or arylalkyl, R = H or Me) undergo thermal rearrangement to give the corresponding vinylogous benzothiazoline-2-thiones [==CHC(S)R in the 2-position].  

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Oxidative C—S bond formation (I2, Br2 or SOCl2) converts thioanilides PhNHCSR into benzothiazoles (281) (the Jacobson-Hugershoff synthesis). Thus, ArNHCSCH(C02Et)2 with bromine yields the benzothiazole (282) (73ZC176). 

Jacobson-Hugershoff synthesis benzothiazoles, 5, 135 Japp-KJingemann reaction N-arylhydrazones from, 4, 337 1,2,4-triazole synthesis by, 5, 768 Jasmine lactone synthesis, 3, 847 Jasminine occurrence, 2, 626 y-Jasmolactone synthesis, 4, 674 cis-Jasmone synthesis, 1, 422, 427 Jatropham synthesis, 1, 426 Josephson junctions, 1, 359 Juliprospine occurrence, 4, 477 Julolidine... 

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