Indolyl 3 carbinol

A number of additional cyclizations involving alkynes have been reported. For instance, it has been shown that indoles may also be accessed from 2-bromo- or 2-chloroanilines, as illustrated by the regioselective preparation of the carbinol 373 in the presence of the ferrocene 374 (Equation 104) <20040L4129>, whereas a one-pot sequence featuring titanium catalyzed hydroamination of 2-chloroanilines with acetylenes, followed by intramolecular Heck cyclization in the presence of an imidazol-2-ylidene palladium complex, has also been reported <2004CC2824>. A set of aryl-2-indolyl carbinols have been prepared in high enantiomeric purity by palladium-catalyzed annulation of... 

An interesting reactivity comparison was carried out with l-(l-methyl-2-indolyl)-l-(jV-methyl-2 -pyrrolyl)ethene 57 obtained via the corresponding carbinol. An inspection of its structure suggests that the molecule could react in a cycloaddition reaction as a vinylindole or as a 2-vinylpyrrole. In reactions with dienophiles, which include DMAD, it reacted as a 2-vinylindole, affording a carbazole derivative 58 (89JHC1869). 

Bader and Oroshnik (142) hydrogenated a-(3-indolyl)-2-pyridine-methanol in the presence of platinum oxide in alcohol solution containing a considerable excess of acetic acid. They obtained 3.5% of the piperidine carbinol and 51% of 2-skatylpiperidine [2-(3-indolylmethyl)-piperidine] showing that the indole ring remained intact. The same authors (143) showed that 4-skatylpyridine was converted to 4-skatylpiperidine. 

A Nazarov cyclization of the enone 151 was used to synthesize analogs of yuehchukene. The cyclization reaction proceeds in 83% yield. After reduction of the corresponding carbinol, reaction with indole in the presence of BF, introduces the indolyl substituent with trans stereoselectivity. <94SC65>... 

Figure 2.3 Indolyl glucosinolates derived from tryptophan. These occur in most cruciferous vegetables, and degrade to a number of non-sulphur-containing degradation products, lndolyl-3-carbinol can conjugate with acetic acid to form ascorbigen.

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