Tertiary amides ortholithiation

Epoxides will also capture organolithiums formed by deprotonation, notably cyclopropyllithiums and ortholithiated tertiary amides. Ortholithiated amides cyclise regioselectively in a valuable route to benzofurans such as 142 and 143 and (less efficiently) benzopyrans 144.70... 

Even sulphonate esters 109 are powerful directing groups, competing well with tertiary amides. No substitution accompanies ortholithiation of ethyl or isopropyl benzene-sulphonate by BuLi. Hydrolysis and chlorination of the products 110 gives functionalized sulphonyl chlorides 111 (Scheme 48) °°. 

The amide 504 may be made by ortholithiation of benzodioxolane 505, though a higher-yielding preparation starts from 1,2-dihydroxybenzoic acid 506. OrthoUthiation of 504, directed by the tertiary amide group, is straightforward, and gives the alkylated amide 503 (Scheme 196). 

Tertiary amides can direct vinylic lithiations in the manner of ortholithiations as shown by the example of 605 and 606. Even methyl groups can be lithiated given an appropriate director and base 607 forms the cyclopropane 609 on treatment with 608 in refluxing heptane (Scheme 238). ... 

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