Pyrroles regiocontrolled

Yoshida K (1979) Regiocontrolled anodic cyanation of nitrogen heterocycles. Pyrroles and indoles. J Am Chem Soc 101 2116-2121... 

A rhodium-catalyzed transannulation of tosyl-triazoles 9 with silyl or alkyl enol ethers 10 was developed that allows for the synthesis of substituted pyrroles 11 with regiocontrol.The addition ofTsOH promotes the final dehydration step to afford pyrroles with different functionality. The method can also be adjusted to allow for the synthesis of 3-pyrrolin-2-ones by using silyl ketene acetals as one of the coupling partners (14TL6455). 

Michael addition of heteroaromatics (indole, pyrrole, thiophene, or furan) to 3-methyl substituted 2-quinonyl boronic acids has been shown to proceed at the boron-substituted C=C bond, followed by a spontaneous protodeboronation. The B(0H)2 group thus acts as a temporary regiocontroller, further activating the adjacent C=C bond.3 o... 

Scheme 8.7 The regiocontrolled formation of pyrroles via a formal [3+2] cycloaddition of isocyanides and electron-deficient alkynes.

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