Simmons-Smith reaction

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The Simmons-Smith reaction is a name reaction in organic chemistry that was named after its developers Howard E. Simmons and Ronald D. Smith . It is used for the synthesis of derivatives of cyclopropane and is an addition reaction , whereby a carbene is added to a double bond without free carbene being present in the reaction mixture.

Overview reaction

An alkene reacts with the reagents diiodomethane and zinc to form cyclopropane and zinc iodide .

Overview of the Simmons-Smith reaction

mechanism

First , a zinc carbene ( carbenoid ) is produced from diiodomethane and excess activated zinc , which can be obtained by using the zinc-copper pair . This organozinc compound is comparable to the Grignard compound . Depending on the solvent, the substrate has a different structure, which corresponds to the Schlenk equilibrium in the Grignard reaction .

Mechanism of the Simmons-Smith reaction

In the next reaction step , the carbenoid reacts with an alkene . The methylene group of the carbenoid adds to the double bond of the alkene in a concerted reaction. In a transition state, electrons are shifted, resulting in cyclopropane and zinc iodide .

Mechanism of the Simmons-Smith reaction

The Simmons-Smith reaction is stereospecific . This means that when using cis -alkenes cis -cyclopropane derivatives are obtained and when using a trans -alkene the corresponding trans -derivatives are obtained. Instead of the zinc-copper pair, diethyl zinc can also be used as a source of zinc.

If the alkene used contains a functional group at a chiral center which can coordinate with zinc ions , stereo information can be induced via this, which leads to the preferred formation of a stereoisomer.

Stereoselective formation of a cyclopropane ring on a cyclohexene

The attack from this side can be prevented by sterically demanding residues and the cyclopropanation preferably takes place from the other side.

Asymmetric Simmons-Smith reaction

The Simmons-Smith reaction can also be carried out enantioselectively by using chiral ligands . This was first achieved in 1992 using chiral disulfonamide ligands.

use

The Simmons-Smith reaction is used, for example, to make spiro compounds. The figure shows the synthesis of rattan.

Using the Simmons-Smith reaction

Another application is the indirect α- methylation of ketones .

literature

T. Laue, A. Plagens: Name and keyword reactions . 4th edition, Teubner, Wiesbaden 2004, ISBN 3-519-33526-3 .

Individual evidence

  1. ^ HE Simmons Jr., RD ​​Smith: A new Synthesis of Cyclopropanes from Olefins , in: J. Am. Chem. Soc. 1958 , 80 , 5323-5324.
  2. ^ HE Simmons, RD Smith: A New Synthesis of Cyclopropanes , in: J. Am. Chem. Soc. 1959 , 81 , 4256-4264.
  3. ↑ T. Laue, A. Plagens: Name and catchword reactions of organic chemistry . Teubner Verlag, 2006, ISBN 3-8351-0091-2 , p. 307-309 .
  4. ^ AB Charette, H. Lebel: (2S, 3S) - (+) - (3-phenylcyclopropyl) methanol In: Organic Syntheses . 76, 1999, p. 86, doi : 10.15227 / orgsyn.076.0086 ; Coll. Vol. 10, 2004, p. 613 ( PDF ).
  5. ^ Y. Ito: One-Carbon Ring Expansion of Cycloalkanones to Conjugated Cycloalkenones: 2-Cyclohepten-1-one In: Organic Syntheses . 59, 1979, p. 113, doi : 10.15227 / orgsyn.059.0113 ; Coll. Vol. 6, 1988, p. 327 ( PDF ).
  6. ↑ Grieco et al. J. Org. Chem. 1977 , 42 , 4113.
  7. ↑ HE Simmons, Org. React. 1973 , 20 , 1.
  8. ↑ H. Takahashi, M. Yoshioka, M. Ohno, S. Kobayashi: A catalytic enantioselective reaction using a C 2 -symmetric disulfonamide as a chiral ligand: cyclopropanation of allylic alcohols by the Et 2 Zn-CH 2 I 2 -disulfonamide system , Tetrahedron Lett. 1992 , 33 , 2575-2578.
  9. ↑ T. Laue, A. Plagens: Name and catchword reactions of organic chemistry . Teubner Verlag, 2006, ISBN 3-8351-0091-2 , p. 307-309 .

Web links

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