Benzothiazo lines

Stabilization of a metal-substituted derivative of a minor tautomeric form of the Ugand was reported for the complexes of mixed benzothiazo-line-benzimidazole (388 —> 389) (71ZOB1370 98POL381) and benzothia-zoline-pyridine ligands (390 —> 391/392) (Scheme 144) (77JA7704). 

The 1,3,5-benzothiadiazepine system (561) has recently been prepared for the first time via methylation of the sulfimide (560 R = CH2Ph) with trimethyloxonium fluoroborate. The rearrangement did not take place however when R = Me or when alkyl halides were used as alkylating agents. The product (561) rearranged readily in acid to give a benzothiazo-line (79JCR(S)214>. 

Aryl groups in the 2-position hinder dimerization and the polarographic reduction of 2-aryl-3-methylbenzothiazolylium perchlorate (79) yields the corresponding benzothiazo-line (80 Scheme 46). M... 

F. Ribes, R. Guglielmetti, and J. Metzger, Synthesis of bifunctional spiropyrans of benzothiazo-lines and indolines, Bull. Soc. Chim. Fr. 1972, 143 47. 

Similar reactions have been used extensively in the formation of macrocyclic compounds. Imine or Schiff base complexes (RiN=CHR2) have been studied. In this case, the compounds can be formed without complexation, but the reaction is much faster in the presence of metal ions (Figure 12.18). In the absence of the Ni(II) complex, benzothiazo-line is favored in the final step, rather than the imine very little Schiff base is present at equilibrium. 

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