Indolines from oxindoles, isatins, and indoxyls

An important route to indoles is the conversion—usually by reduction or the equivalent manipulation—of oxindoles, isatins, and indoxyls, the most common involving oxindoles [1,2], 

After a less-than-auspicious start [10, 11], researchers soon realized that boron hydrides do reduce oxindoles to 

Indole Ring Synthesis From Natural Products to Drug Discovery, First Edition. Gordon W. Gribble. 2016 John Wiley Sons, Ltd. Published 2016 by John Wiley Sons, Ltd. 

A second important and widely used reaction of oxindoles is activation of the carbonyl group with POClj (POBrj) or acid chlorides, followed by subsequent chemistry at C-2. There is a vast literature on this reaction  

Other synthetic applications of indoline-2-thiones include the synthesis of lhiopyrano[2,3-( ]indoles and thieno[2,3-i ]indoles [78-80], S-alkylated indoles [81, 82], thiopyrano[2,3-i 6,5-fc ]diindoles [83], and thiacarbazol-2(97/)-ones [84]. Bergman and Janosik oxidized thiooxindole with p-toluenesulfonyl azide to produce a trimer that apparently forms via a thiooxindole carbine [85]. Thiooxindoles are usually desulfurized to indolines and/or indoles with Raney nickel [20]. 

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