Diazo compounds decomposition

Carbenes from Diazo Compounds. Decomposition of diazo compounds to form carbenes is a quite general reaction that is applicable to diazomethane and other diazoalkanes, diazoalkenes, and diazo compounds with aryl and acyl substituents. The main restrictions on this method are the limitations on synthesis and limited stability of the diazo compounds. The smaller diazoalkanes are toxic and potentially explosive, and they are usually prepared immediately before use. The most general synthetic routes involve base-catalyzed decomposition of V-nitroso derivatives of amides, ureas, or sulfonamides, as illustrated by several reactions used for the preparation of diazomethane. 

The metal-catalyzed decomposition of diazo compounds has broad applications in organic synthesis [1-8]. Transient metal carbenoids provide important reactive intermediates that are capable of a wide variety of useful transformations, in which the catalyst dramatically influences the product distribution [5]. Indeed, the whole field of diazo compound decomposition was revolutionized in the early 1970s with the discovery that dirhodium tetracarboxylates 1 are effective catalysts for this process [9]. Many of the reactions that were previously low-yielding using conventional copper catalysts were found to proceed with unparalleled efficiency using this particular rhodium catalysis. The field has progressed extensively and there are some excellent reviews describing the breadth of this chemistry [5, 7, 10-17]. 

The use of chiral copper complexes in diazo-compound decompositions is a known route to optically active cyclopropanes and the potential of this process has been further exemplified. ... 

Chiral cyclopropanes are important compounds found in biologically active molecules. As efficient synthesis for these compounds are in demand many asymmetric cyclopropanation methods have been developed. Among these, cyclopropanation with diazo compound decomposition is outstanding. 

Diazo Compounds Decomposition with Chiral Copper Catalysts. One of the important developments in copper-catalyzed cyclopropanation concerns the asymmetric version of the reaction. Although enantioselectivity was low... 

Diazo Compounds Decomposition with Chiral Rhodium Catalysts. The first chiral rhodium catalyzed asymmetric cyclopropanation was reported in 1989 (75). Structures of the catalysts were based on the framework of dirhodium(II) tetrakis(carboxylate) 1 with the carboxylate ligands replaced with... 

---