Methylene-selective C–H functionalization is a significant hurdle that remains to be addressed in the field of Pd(II) catalysis. We report a Pd(II)-catalyzed synthesis of benzocyclobutenes by methylene-selective C(sp³)–H arylation of ketones. The reaction utilizes glycine as a transient directing group and a 2-pyridone ligand, which may govern the methylene selectivity by making intimate molecular associations with the substrate during concerted metalation–deprotonation. This reaction is shown to be highly selective for intramolecular methylene C(sp³)–H arylation, thus enabling sequential C(sp³)–H functionalization.

中文翻译：

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Pd(II)-催化β-亚甲基选择性C(sp3)-H芳基化与瞬态导向基团合成苯并环丁烯

亚甲基选择性 C-H 官能化是 Pd(II) 催化领域仍有待解决的重大障碍。我们报告了通过酮的亚甲基选择性 C(sp ³ )-H 芳基化合成苯并环丁烯的 Pd(II) 催化。该反应利用甘氨酸作为瞬态导向基团和 2-吡啶酮配体，这可以通过在协同金属化-去质子化过程中与底物形成紧密的分子结合来控制亚甲基的选择性。该反应被证明对分子内亚甲基 C(sp ³ )-H 芳基化具有高度选择性，因此能够实现连续的 C(sp ³ )-H 官能化。