By the Simmons-Smith reaction

The preparation of [5]rotane 81 (pentaspiro[2.0,2.0.2.0.2.0.2.0]pentadeeane), again includes one step of carbene addition, by the Simmons-Smith reaction, to 13-methyle-ne-tetraspiro[2.0.2.0,2.0.2.1]tridecane 8026). A full paper on the subject appeared later 27 >. 

Diphenylcyclopropane has been prepared in 24% yield by the Simmons-Smith reaction,2 in 78% yield by treatment of 3,3-diphenylpropyltrimethylammonium iodide with sodium or potassium amide,3 in 61% yield by reaction of 1,1-diphenyl-ethylene with dimethylsulfonium methylide,4 and in unspecified yields from 1,1-diphenylethylene by reaction with diazomethane followed by pyrolysis of the resulting pyrazoline or by reaction with ethyl diazoacetate followed by distillation of the corresponding acid over calcium oxide.5... 

Table 1. Siloxycyclopropanes prepared by the Simmons-Smith reaction...

Asymmetric cyclopropanation of olefins can also be achieved by the Simmons-Smith reaction (231). Reaction of ( )-cinnamyl alcohol and the diiodomethane-diethylzinc mixed reagent in the presence of a small amount of a chiral sulfonamide gives the cyclopropylcarbinol in up to 75% ee (Scheme 97) (232a). ( )-Cinnamyl alcohol can be cyclopro-... 

The cyclopropanes are prepared either by reduction of the gem-dibrominated derivates with Bu3SnH by either the method of Seyferth (24) or by the Simmons-Smith reaction. 

Polymerization. Monomers. The cyclopropane type monomers are prepared either by addition of the dichlorocarbene or by the Simmons-Smith reaction on the corresponding olefins. Most of these compounds have been described. Spiropentane is prepared by the Applequist method (I, 2), by the reaction of zinc with C(CH2Br)4 in alcohol in the presence of ethylenediaminetetraacetic acid (EDTA). This hydrocarbon is purified until a single NMR signal is obtained at t = 9.28. 

A cis addition mechanism is generally accepted for the reaction, because cis addition to an olefinic bond generally occurs with predominant attack at trans bonds, and the Simmons-Smith reagent attacks preferentially one of the trans olefinic bonds of trans,trans,cis-1,5,9-cyclodode-catriene and then the cis double bond of the monoadduct (378). The close correspondence in relative rates of olefins for the cyclopropane formation by the Simmons-Smith reaction with those for diimide reduction and peroxide epoxidation supports the concept 409). The latter two reactions are generally considered to proceed via cis addition. 

Duodomethane. 13,110-115 275-276 16,184-185 17,155 18, 139-140 19,128 Cyclopropanation. 1-Alkenylsilanols are transformed into cyclopropylsilanols by the Simmons-Smith reaction. A Grignard reagent may replace the zinc or diethylzinc... 

A variety of other unsaturated sugars have been converted into cyclopropane derivatives by addition of dihalocarbene generated in the usual way, or by the Simmons-Smith reaction. 

The enormous potential provided by the Simmons-Smith reaction is further demonstrated in an efficient one-pot synthesis of spiro-compounds of the type (10) by reaction of cyclic enol-silyl ethers with diethylzinc-methylene iodide this remarkable synthesis ca. 70% overall) proceeds via the three sequential reactions (7) (8), (8) (9), and (9)— (10). The versatile dichlorocarbene species is most conveniently generated under phase-transfer conditions using either KOBu -crown or NaOH-PhCHzNEts Cl. 

Cyclopropanes can be made stereoselecfively by the Simmons-Smith reaction. Diiodomethane, zinc and an alkene are heated together in ether. The intermediate is probably ICH Znl. 

This reaction is called the Smmons-Smith reaction and is one of the few methods avail able for the synthesis of cyclopropanes Mechanistically the Simmons-Smith reaction seems to proceed by a single step cycloaddition of a methylene (CH2) unit from lodomethylzmc iodide to the alkene... 

By application of the Simmons-Smith reaction it is possible to synthesize a cyclopropane from an alkene by formal addition of carbene to the carbon-carbon double bond, without a free carbene being present in the reaction mixture the... 

A carbene, R2C , is a neutral molecule containing a divalent carbon with only six valence electrons. Carbenes are highly reactive toward alkenes, adding to give cyclopropanes. Nonlialogenated cyclopropanes are best prepared by treatment of the alkene with CH212 and zinc-copper, a process called the Simmons-Smith reaction. 

The Simmons-Smith reaction has been used as the basis of a method for the indirect a methylation of a ketone. The ketone (illustrated for cyclohexanone) is first converted to an enol ether, an enamine (16-12) or silyl enol ether (12-22) and cyclopropanation via the Simmons-Smith reaction is followed by hydrolysis to give a methylated ketone. A related procedure using diethylzinc and diiodomethane allows ketones to be chain extended by one carbon. In another variation, phenols can be ortho methylated in one laboratory step, by treatment with Et2Zn and... 

Chemo- and stereoselective reduction of (56) to (55) is achieved In highest yield by sodium borohydride in ethanol. The isolated ketone is reduced more rapidly than the enone and (55) is the equatorial alcohol. Protection moves the double bond out of conjugation and even the distant OH group in (54) successfully controls the stereochemistry of the Simmons-Smith reaction. No cyclopropanation occurred unless the OH group was there. Synthesis ... 

In a new version of the Simmons-Smith reaction allyl or aUenic alcohols such as cyclohexenol are converted by Sm/CH2l2/Me3SiCl 14 in THF at -78°C into syn cyclopropanols such as 2135 [63] (Scheme 13.17). 

Several modifications of the Simmons-Smith procedure have been developed in which an electrophile or Lewis acid is included. Inclusion of acetyl chloride accelerates the reaction and permits the use of dibromomethane.174 Titanium tetrachloride has similar effects in the reactions of unfunctionalized alkenes.175 Reactivity can be enhanced by inclusion of a small amount of trimethylsilyl chloride.176 The Simmons-Smith reaction has also been found to be sensitive to the purity of the zinc used. Electrolytically prepared zinc is much more reactive than zinc prepared by metallurgic smelting, and this has been traced to small amounts of lead in the latter material. 

The rhodium acetate catalyzed addition of ethyl diazoacetate to MCP (1) gave spiropentane 619 in high yield (Scheme 89) [6e]. The same compound 619 was obtained in lower yield by a Simmons-Smith reaction to methylenecyclo-propane 217 [164],... 

The Simmons-Smith reaction " and its variants are widely used for the stereospecific synthesis of cyclopropane compounds. The methodology involves the use of copper-treated zinc metal (the zinc-copper couple) with diiodomethane to add methylene to a carbon-carbon double bond. Alternative use of diazomethane in catalytic reactions does not offer the same synthetic advantages and is usually avoided because of safety considerations. As significant as is the Simmons-Smith reaction for cyclopropane formation, its employment for organic synthesis was markedly advanced by the discovery that allylic and homoallylic hydroxyl groups accelerate and exert stereochemical control over cyclopropanation of alkenes (e.g, Eq. 21), and this acceleration has been explained by a transition state model... 

Preparation of spiro[2.3]hexanes is possible by the addition of methylene or a methylene equivalent to an exocyclic C —C double bond. Generally, the Simmons Smith reaction is used (see Section l.A.1.2.1.), but formation of carbenes from nitroso compounds can also be used.73-75,333 The 1,1-dihalo derivative can be prepared by phase-transfer-catalyzed reactions.48 For example, reaction of a mixture of cis- and trans-1,2-dimethyl-3-methylenecyclobutane with dibromo-carbene gave a mixture of cis- and lrans-1,1-dibromo-4,5-dimcthylspiro[2.3]hexanc (2).48... 

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