Oxindoles, azaindoles, and carbazoles

A radical cyclization approach to spiro-oxindoles was revealed 05OL151 . Treatment of p-trityloxybenzamide 125 with triethylborane and tris(trimethylsilyl)silane gave cyclohexadienone 126 via an ipso cyclization. The nucleophilic aromatic substitution of aryl fluorides was utilized in an asymmetric approach to spiro-pyrrolidone oxindoles 05JA3670 . 

This paragraph details carbazole syntheses that involve the formation of new bonds to nitrogen. A direct C-H functionalization/amination of 2-acetaminobiphenyl compounds give carbazoles in one step 05JA14560 . For example, treatment of biphenyl 130 with palladium acetate and copper(II) acetate gave carbazole 131. A short s)mthesis of carbazoles involved the reductive cyclization of 2-nitrobiphenyl compounds mediated by triphenylphosphine 

The final paragraph in this section details carbazole syntheses that involve the formation of C-C bonds. Intramolecular Diels-Alder cycloaddition of ynamides provided a new route to [b -fused carbazoles 05OL2213 . An electrocyclization of 2,3-divinylindole intermediates produced functionalized carbazoles 05TL4045 . A domino alkynylation/palladium migration/C-H activation approach to 4-vinylcarbazoles was reported 050L701 . For example, treatment of A-arylaniline 134 with diphenylacetylene in the presence of palladium acetate, cesium pivalate (CsPv), and bis(diphenylphosphino)methane (dppm) gave carbazole 136 via post-palladium migration intermediate 135. 

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As with the corresponding section on p3rroles, indole syntheses have been categorized utilizing a systanatic approach. Intramolecular approaches (t)rpe I) and intermolecular approaches (type II) are classified by the number and location of the new bonds that describe the indole forming step (2 examples shown below). In addition, the synthesis of oxindoles, azaindoles, and carbazoles wUl be treated separately. 

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