Stannyl indoles

Methyl-2-(tri-n-butyl-stannyl)indole 4-Bromobenzonitrile, Pd(PPh3),Cl, 91 [2]... 

Fukuyama s tin-mediated indole synthesis was also highlighted in the enantio-selective total synthesis of aspidophytine [45]. Treatment of the 2-alkenylphenyli-sonitrile 54 with tributyltin hydride and AIBN in refluxing acetonitrile followed by treatment of the 2-stannyl indole intermediate with iodine gave the expected 2-iodoindole 55, bearing methoxy groups at C-6 and C-7 of the indole ring, in 85% yield. 

The Fukuyama indole synthesis was used during the total synthesis of aspidophytine 28. Tin-mediated indole formation was followed by the treatment of the 2-stannyl indole intermediate with iodine and gave the 2-iodoindole derivatives 27 in 85% yield. ... 

Widdowson expanded his hexacarbonylchromium chemistry to the synthesis and lithiation of Cr(CO)3-Af-TIPS indole (29), leading to 4-iodoindole 30 after oxidative decomplexation [37]. Stannylation at C-4 could also be achieved using this method (62% yield), and comparable chemistry with 3-methoxymethylindole leading to C-4 substitution was described. 

Stille couplings also have been exploited in the synthesis of the aromatic macrocyclic core of diazonamide A (2) [5, 20]. Pattenden s group utilized the Pd-catalyzed coupling between the 3-stannyl substituted indole 23 and the 3-bromooxazole 24 to provide a particularly expeditious route to the ring system 25 [20]. In addition, Harran s group secured the connection between bromooxazole 12 and vinylstannane 26 also using a Stille coupling [5]. 

The indole 836, the product of -substitution in the Stille reaction of the 3-iodoindole 834 with the trimethyl-stannyl derivative of imidazole 835, was obtained as shown in Equation 211 <1998H(48)11>. 

The same 43/water biphasic system efficiently works for the Michael addition of indoles to a,P-unsaturated enones, the Mannich reaction in its one-pot three-component version, the allyl stannylation of carbonyl compounds and the asymmetric hydroxymethylation of silylenolethers. The last reaction (Figure 45) is carried out in the presence of the chiral bipyridine 45. ... 

Useful alternative preparations of stannanes include palladium-catalysed decarboxylation of stannyl esters. ° Trialkylstannyl and trialkylsilyl anions are highly reactive and will displace halogen without the use of a catalyst. It is possible to directly silylate indoles and pyrroles via electrophilic substitution. ... 

With this substrate (28) the ring closure can be conveniently accomplished with either stannyl or sulfanyl radicals with no concomitant formation of the six-membered-cyclization quinoline product, which is present instead, or is predominantly formed, in all of the reaction mixtures obtained with group other than TMS. At the same time, both radical precursors, that is, stannane and thiol, can serve as nucleophiles for the intermediate indolenines 29 and 31, which are trapped to give the final substituted indoles 30 and 32 with high efficiency. 

When an organometallic derivative of indole is required for a coupling reaction, boronic acids are to be preferredalthough 2-zinc and 2-stannyl derivatives can be used. The palladium-catalysed coupling of 6-bromo or 6-iodoindoles with allyl and heteroaryltin compounds does not require masking of the indole iV-hydrogen. ... 

Fluorinated indoles can be obtained in good yield from the 2- and 3-stannyl derivatives by reaction with cesiiun fluoroxysulfate (CFS) and methanol <94T1899>. The nitrogen must be protected and the stannyl compounds are prepared by routine exchange of the respective lithio derivatives (Scheme 47). 

Kim T, Kim K (2010) Practical method for synthesis of 2,3-disubstituted indole derivatives promoted by (3-(benzotriazol-l-yl)allylic 0-stannyl ketyl radicals. Tetrahedron Lett 51 868-871... 

A bromo or triflyloxy substituent in the /S-position of the indole can be replaced by stannylation after initial lithiation (Scheme 2). The Al-silyl-protected 3-bromo-7-azain-... 

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