Benzothiazolone, 3-alkyl

Benzothiazolone, 3-alkyl-, 53 2,3-Benzothiepine, chloro-, 74 Benzothiophenes, nucleophilic substitution of, 370... 

The second recent variant, developed by Julia and co-workers, avoids reductive elimination altogether and provides a remarkable one-pot connective synthesis of alkenes. The procedure, illustrated in eq 14, involves condensation of an aldehyde or ketone with a lithiated benzothiazolyl alkyl sulfone to give an adduct which first cyclizes and then fragments with extrusion of sulfur dioxide, benzothiazolone (which then tautomerizes to 2-hydroxybenzothiazole), and the alkene. Generally a mixture of ( )- and (2)-alkenes is obtained, hut in stericaUy hindered substrates the ( ) isomer can be obtained selectively. The same reaction has been observed with the pyridinyl sulfone analogs, in which case the separable /8-hydroxy sulfone intermediates undergo stereospecific and elimination to the corresponding alkene. 

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