The first examples of efficient and general palladium-catalyzed intramolecular C (sp3)− H arylation of (hetero) aryl chlorides, giving rise to a variety of valuable cyclobutarenes, indanes, indolines, dihydrobenzofurans, and indanones, are described. The use of aryl and heteroaryl chlorides significantly improves the scope of C (sp3)− H arylation by facilitating the preparation of reaction substrates. Careful optimization studies have shown that the ...