Nitrocyclopropanes as Valuable Building Blocks in Organic Synthesis and Biology: Exploring the Origin of the Nitro Group.

Cyclopropane derivatives serve as important building blocks in organic synthesis, due to their three-membered stretched ring. Nitro-substituted cyclopropanes (NCPs) represent a special class of donor-acceptor cyclopropanes (DACs) that contain a strong electron-withdrawing nitro group as substituent on the cyclopropyl moiety. Due to the versatile nature of the nitro group, which can be converted into other functional azo groups or heterocyclic scaffolds, NCPs are considered important building blocks in the design of complex organic compounds. Herein, the present review is organized in two main sections focused on the synthesis and application of NCPs. The part containing the synthetic methodologies of NCPs has been further divided into distinct sections based mainly on the nature of the starting materials, such as: a) from nitroalkenes, b) from nitro-bearing diazo compounds, c) from nitroalkanes in combination with alkenes, d) from aminocyclopropanes under oxidative conditions, and e) from various nitro compounds, through miscellaneous processes. In the part concerning the applications and use of NCPs, the categorization includes three main subcategories, concerning their reduction to 1-aminocyclopropane-1-carboxylic acids (ACC), the ring opening of NCPs leading to valuable open-chain heterocycles, and the ring expansion to larger cyclic and heterocyclic compounds.