Alkane functionalization: Recent advances

Despite the progress of alternative/renewable energy technologies (solar, wind, hydroelectric, geothermal, nuclear, hydrogen, bio, tidal and wave), still the fossil raw materials such as petroleum (crude oil), natural gas and coal remain the main source of energy. The major constituents of crude oil (ca. 20-50 %) and natural gas (ca. 95 % methane, 4 % ethane, 0.2 % propane and 0.02 % butane) are alkanes, which are stable molecules due to high bond dissociation enthalpy of C-sp3 - H (96-105 kcal/mol) and C-sp3 - C-sp3 (83-90 kcal/mol) bonds. Due to the low cost and high richness in carbon, alkanes are fundamental feedstocks in chemical industry and starting materials in the synthesis of value-added products. In contrast to unselective classic radical mechanism, the metal complex catalysed direct activation of chemical inert C-sp3 - H and C-sp3 - C-sp3 bonds in alkanes concerns extremely important synthetic transformations with high economic impact. This review is aimed to provide an overview on recent (2019-2023) advances in homogenous metal free and metal complex catalysed activation and functionalization of alkanes leading to CC or C-sp3 - Element bonds. Instead of a comprehensive review, herein a special attention is focused on selected new synthetic strategies and reaction mechanisms in C-sp3 - H functionalization in alkanes.