Sie dient der Synthese von Derivaten des Cyclopropans und ist eine Additionsreaktion, wobei ein Carben an eine Doppelbindung addiert wird, ohne dass freies Carben im Reaktionsgemisch vorhanden ist. Reagent in Simmons-Smith cyclopropanation reactions. reagents for the cyclopropanation of unfunctionalized alkenes.24 Several other structures of zinc carbenoids, such as those of MeOZnCH 2I25 and (PhC(O)OCH 2) 2Zn,26 were recently resolved, but these reagents are quite unreactive toward alkenes unless they are activated (vide infra). Regioselective ring cleavage of chiral β-trichloromethyl-β-propiolactone with organoaluminum compounds for the synthesis of optically … Simmons–Smith Cyclopropanation : Named Reactions in Organic Synthesis Reaction category: Electrophilic addition reactions Other featured reactions: Noyori asymmetric hydrogenation; Prilezhaev reaction; Schwartz hydrozirconation; Shi asymmetric epoxidation . Die Simmons-Smith-Reaktion ist eine Namensreaktion in der Organischen Chemie, die nach ihren Entwicklern Howard E. Simmons und Ronald D. Smith benannt wurde. Studies into the Reactivity of Alkyl-Substituted Zinc Carbenoids, Effect of Directing Groups and Synthesis of Bicyclo[ n .1.0]alkanes , Journal of the American Chemical Society , 10.1021/ja907504w , 132 , 6 , … Synthetic Communications 1999, 29 (11) , 1889-1902. [full procedure] Procedure excerpt: To a solution of diethylzinc (1.0M in hexane, 46 mL, 46 mmol) in DCM (200 mL) was added dropwise a solution of TFA (3.54 mL, 46 mmol) in DCM (50 mL) at 0 C over 30 min. Simmons-Smith Reaction This reaction affords the cyclopropanation of olefins. Diastereoselective Simmons–Smith cyclopropanations of allylic amines and carbamates . DOI: 10.1080/00397919908086177. The chemoselectivity of the reaction toward some olefins is … The Simmons–Smith reaction is generally subject to steric effects, and thus cyclopropanation usually takes place on the less hindered face. Cyclopropanation refers to any chemical process which generates cyclopropane rings. Tamotsu Fujisawa, Takatoshi Ito, Shin Nishiura, Makoto Shimizu. . For … . Stephen G. Davies,* a Kenneth B. Ling, a Paul M. Roberts, a Angela J. Russell a and James E. Thomson a Author affiliations * Corresponding authors a Department of Organic Chemistry, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford, UK E-mail: [email protected]. James A. La cyclopropanation de Simmons-Smith est une réaction concertée dont l'état de transition le plus probable est de type papillon. The Simmons–Smith reaction is a powerful method for preparing cyclopropanes from olefins using zinc carbenoids (IZnCH 2 I, EtZnCH 2 I, Zn (CH 2 X) 2). Here I chart the course of the cyclopropanation of alkenes using the Simmons-Smith reagent, as prepared from di-iodomethane using zinc metal insertion into a C-I bond.

This popularity is mainly due to the stereospecificity of the reaction with respect to the double bond geometry and its compatibility with a wide range of functional groups.

It uses a methylene free radical intermediate that is delivered to both carbons of the alkene simultaneously, therefore the configuration of the double bond is preserved in the product and the reaction is stereospecific. Nowadays, the Simmons‐Smith cyclopropanation reaction is one of the most widely used reactions in the organic chemist's arsenal for the conversion of olefins into cyclopropanes. Asymmetric Simmons-Smith Cyclopropanation Of α,β-Unsaturated Bornane-2,3-Diol Acetals. . Two reactions it can be compared with are the epoxidation of ethene using a peracid and dichlorocyclopropanation.

It is named after Howard Ensign Simmons, Jr. and Ronald D. Smith. This species is an example of a carbenoid or carbene-like substance, because, like carbenes, it also converts … Mechanism of the Simmons-Smith Reaction Ultrasonication improves the rate of formation of these organozinc compounds, as with many organometallic reactions occurring at a surface.

Simmons-Smith reagent, ICH 2 ZnI 2 is obtained when diiodomethane is treated with zinc powder (usually activated with copper). Bull and André B. Charette, Intramolecular Simmons−Smith Cyclopropanation.