Catalytic Reductive N-Alkylations Using CO2 and Carboxylic Acid Derivatives: Recent Progress and Developments.

N-Alkylamines are key intermediates in the synthesis of fine chemicals, dyes, and natural products, and hence are highly valuable building blocks in organic chemistry. Consequently, the development of greener and more efficient procedures for their production continues to attract the interest of both academic and industrial chemists. Reductive procedures such as reductive amination or N-alkylation through hydrogen autotransfer by employing carbonyl compounds or alcohols as alkylating agents have prevailed for the synthesis of amines. In the last few years, carboxylic/carbonic acid derivatives and CO2 have been introduced as alternative and convenient alkylating sources. The safety, easy accessibility, and high stability of these reagents makes the development of new reductive transformations with them as N-alkylating agents a useful alternative to existing procedures. In this Review, we summarize reported examples of one-pot reductive N-alkylation methods that use carboxylic/carbonic acid derivatives or CO2 as alkylating agents.