Simmons-Smith reaction

The Simmons-Smith reaction is an organic reaction in which a carbenoid reacts with an alkene (or alkyne) to form a cyclopropane.^[1][2][3] Thus, cyclohexene, diiodomethane, and a zinc-copper couple (as (iodomethyl)zinc iodide, ICH₂ZnI) yield bicyclo[4.1.0]heptane.^[4][5]

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Alternatively, diethylzinc is used instead of the zinc-copper couple.

The Simmons-Smith reaction is generally subject to steric effects, and thus cyclopropanation usually takes place on the less hindered face.^[6][7] However, when hydroxy substituents are present on chiral carbons, the zinc coordinates with the hydroxy substituents, directing cyclopropanation to the same face, which may or may not be sterically favorable ^[8]:

The Simmons-Smith reagent, namely diiodomethane and diethylzinc, can be react with allylic thioethers to generate sulfur ylides, which can subsequently undergo a 2,3-sigmatropic rearrangement, and will not cyclopropanate an alkene in the same molecule unless excess Simmons-Smith reagent is used^[9]:

References

1. ^  Simmons, H.E.; Smith, R.D. J. Am. Chem. Soc., 1958, 80, 5323.
2. ^  Simmons, H.E.; Smith, R.D. J. Am. Chem. Soc., 1959, 81, 4256.
3. ^  Denis, J.M.; Girard, J.M.; Conia, J.M. Synthesis, 1972, 549.
4. ^  Smith, R. D.; Simmons, H. E. Organic Syntheses, Coll. Vol. 5, p.855 (1973); Vol. 41, p.72 (1961). (Article)
5. ^  Ito, Y.; Fujii, S.; Nakatuska, M.; Kawamoto, F.; Saegusa, T. Organic Syntheses, Coll. Vol. 6, p.327 (1988); Vol. 59, p.113 (1979). (Article)
6. ^  Simmons, H. E. et al. Org. React. 1973, 20, 1. (Review)
7. ^  Girard, C.; Conia, J. M. J. Chem. Res. (S) 1978, 182. (Review)
8. ^  Grieco et al. J. Org. Chem. 1977, 42, 4113.
9. ^  Cohen, T.; Kosarych, Z. J. Org. Chem. 1982, 47, 4005.