Transformation of carbon dioxide (CO2) into valuable organic carboxylic acids is essential for maintaining sustainability. In this review, such CO2 thermo-, photo- and electrochemical transformations under 3d-transition metal catalysis are described from 2017 until 2022.

Direct utilization of CO2 into organic synthesis has found enormous applications to synthesize pharmaceuticals and fine chemicals. However, pure CO2 gas is essential to achieve these transformations, and the purification of CO2 is highly cost and energy intensive. Considering this, we have described a straightforward synthetic route for the synthesis of γ-lactams, a pivotal core structure of bioactive molecules, by using commercially available starting materials (alkenes and amines) and impure CO2 stream (exhaust gas collected from the car) as the carbon source. This blueprint features a broad scope, excellent functional group compatibility and has been applied for the late-stage transformation of existing pharmaceuticals and natural products to synthesize functionalized γ-lactams. We believe that our strategy will provide direct access to γ-lactams in a very sustainable way and will also enhance the Carbon Capture and Utilization (CCU) strategy.

Linear aliphatic primary amines are crucial and every year, at least, millions of tonnes are required to meet this demand. Therefore, significant interest has been shown in finding new chemical routes for the synthesis of aliphatic primary amines. However, to comply with the sustainability requirements, synthetic routes using inexpensive feedstocks are highly prioritized. In this regard, the hydroaminoalkylation (HAA) reaction, i.e. functionalization of an olefin with an aminoalkyl group and a hydrogen atom across the C=C double bond, is desirable due to the wide availability and lower price of olefins. Although photoredox catalysis is already known to synthesize amines, the synthesis of linear aliphatic amines is only limited to hydroaminomethylation (HAM) reactions i.e. functionalization of an olefin with an aminomethyl group and has never been applied to the synthesis of long chain linear aliphatic primary amines. Considering this, the synthesis of functionalized linear aliphatic primary amines is demonstrated by using a novel photoredox-mediated decarboxylative hydroaminoalkylation reaction, which exhibited a wide scope with excellent yields. The strength of this method is demonstrated by drug synthesis, late-stage modifications of complex pharmaceuticals and elaborated with detailed mechanistic studies.