Anilines lateral lithiation

Much more versatile than the simple anilines are their anilide derivatives. PivalaniUdes, benzanilides and other non"° (or scarcely ) enolizable amides 549 are laterally lithiated on treatment with two equivalents of BuLi, and may be quenched with electrophiles to give 551. In the absence of an electrophile, the organoUthiums 550 cyclize to indoles 552 (Scheme 218). 

The carbamates 459 (R = Or-Bu) behave similarly, though they must be lithiated with s-BuLi to avoid addition to the carbonyl group.418 It is possible simply to use a lithium carbamate to protect an amino group during a lateral lithiation an initial deprotonation and carbonation generates the lithium carbamate 466, which is then deprotonated twice more by r-BuLi. After electrophilic quench, acid hydrolysis of the carbamic acid returns the unprotected aniline.419 420 An alternative in situ protection sequence relies on temporary trimethylsilylation of the aniline.421... 

Gschwend reported the ortho lithiation of aniline pivalamides and subsequent addition to nitriles and carbonyls in 1979. A few years later, Wender used a similar aryllithium (11), obtained by metal-halogen exchange, in a new synthesis of indoles (Scheme 7). An analogous metalation occurs when N-phenylimidazol-2-ones are treated with LDA in THF at -78 C. ... 

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