Diiodomethane reaction

The reaction itself works by the action of Na or K from NaOH or KOH which form what is called a catechoxide dianion with the two OHs of the catechol species. This makes the two ripe for an attack by a methylene halide which can be either DCM (methylene chloride, or dichloromethane), DBM (methylene bromide, or di-bromomethane) or DIM (methylene iodide, or diiodomethane). DCM is cheap and works pretty well, but DBM and DIM work better yet are more expensive. 

An organozmc compound that occupies a special niche m organic synthesis is lodo methyhinc iodide (ICH2ZnI) It is prepared by the reaction of zinc-copper couple [Zn(Cu) zinc that has had its surface activated with a little copper] with diiodomethane m diethyl ether... 

Without question, the most powerful method for cyclopropane formation by methylene transfer is the well-known Simmons-Smith reaction [6]. In 1958, Simmons and Smith reported that the action of a zinc-copper couple on diiodomethane generates a species that can transform a wide variety of alkenes into the corresponding cyclopropanes (Scheme 3.3) [7]. 

Whereas this study focused on reaction protocol, the effect of the methylene source on selectivity was another important factor which demanded attention. Earlier studies have demonstrated that substitution of chloroiodomethane for diiodomethane leads to an increased reaction rate (Scheme 3.10) [22]. It is, thus, surprising that the use of chloroiodomethane in sub-protocol la leads a slower, less selective reaction. In contrast to the use of diiodomethane ( 100% conversion at 300 min), the reaction of chloroiodomethane only reaches 58% conversion after 300 min. Selectivity is severely reduced, dropping to 75 25 er. The failure of this reagent in the chiral process may be attributed to the obvious differences between the highly polarizable iodine and the more electronegative chlorine atom, although an exact analysis of the difference is not clear. 

By reaction of zinc-copper couple with diiodomethane 2 an organozinc species 4 is formed, similar to a Grignard reagent. Its structure cannot be fully described by a single structural formula. The actual structure depends on the reaction conditions—e.g. the solvent used this corresponds to the Schlenk equilibrium as it is observed with the Grignard reaction ... 

Simmons-Smith reaction of cyclohexene with diiodomethane gives a single cyclopropane product, but the analogous reaction of cyclohexene with 1,1-diiodoethane gives (in low yield) a mixture of two isomeric methyl-cyclopropane products. What are the two products, and how do they differ ... 

Dicyclopentadienyltin also takes part in oxidative addition reactions with such reagents as iodomethane, diiodomethane, ethyl bromoace-tate, and diphenyl disulfide, and there is evidence that the reactions involve a radical chain-mechanism (324, 325). 

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... 

In one run that was particularly slow, an additional 9.9 g. of diiodomethane was added. The reaction then proceeded quickly to completion. 

The cyclopropanation of 1-trimethylsilyloxycyclohexene in the present procedure is accomplished by reaction with diiodomethane and diethylzinc in ethyl ether." This modification of the usual Simmons-Smith reaction in which diiodomethane and activated zinc are used has the advantage of being homogeneous and is often more effective for the cyclopropanation of olefins such as enol ethers which polymerize readily. However, in the case of trimethylsilyl enol ethers, the heterogeneous procedures with either zinc-copper couple or zinc-silver couple are also successful. Attempts by the checkers to carry out Part B in benzene or toluene at reflux instead of ethyl ether afforded the trimethylsilyl ether of 2-methylenecyclohexanol, evidently owing to zinc iodide-catalyzed isomerization of the initially formed cyclopropyl ether. The preparation of l-trimethylsilyloxybicyclo[4.1.0]heptane by cyclopropanation with diethylzinc and chloroiodomethane in the presence of oxygen has been reported. "... 

A. N. Tarnovsky, V. Sundstrom, E. Akesson, and T. Pascher, Photochemistry of diiodomethane in solution studied by femtosecond and nanosecond laser photolysis. Formation and dark reactions of the CH2I-I isomer photoproduct and its role in cyclopropanation of olefins. J. Phys. Chem. A 108(2), 237-249 (2004). 

D. L. Phillips, W.H. Fang, and X. Zheng, Isodiiodomethane is the methylene transfer agent in cyclopropanation reactions with olefins using ultraviolet photolysis of diiodomethane in solutions a density functional theory investigation of the reactions of isodiiodomethane, iodomethyl radical, and iodomethyl cation with ethylene. J. Am. Chem. Soc. 123(18), 4197-4203 (2001). 

The reaction can be carried out efficiently using aryl diazonium tetrafluoroborates with crown ethers, polyethers, or phase transfer catalysts.103 In solvents that can act as halogen atom donors, the radicals react to give aryl halides. Bromotrichloromethane gives aryl bromides, whereas methyl iodide and diiodomethane give iodides.104 The diazonium ions can also be generated by in situ methods. Under these conditions bromoform and bromotrichloromethane have been used as bromine donors and carbon tetrachloride is the best chlorine donor.105 This method was used successfully for a challenging chlorodeamination in the vancomycin system. 

Low intensity ultrasound has also been applied to the Simmons-Smith cyclopropanation of olefins with zinc-diiodomethane (237). This reaction normally will not occur without activation of mossy Zn with I2 or Li, and was difficult to scale-up due to delayed initiation. Yields upon sonication are nearly quantitative, activation of the Zn is unnecessary, and no delayed exotherms are observed. In reactions with another class of organic dihalides, ultrasonic irradiation of Zn with a,a -dibromo-o-xylene has proved a facile way to generate an o-xylylene-like species [Eq. (49)],... 

Zinc promoted reactions are responsive to ultrasonic waves. The classic Simmons-Smith reaction was among our first successes(21). Using zinc powder and diiodomethane we obtained good yields of cyclopropanes from styrene and acenaphthene. However, we could not... 

The direct reaction of zinc metal with organic iodides dates back to the work of Frankland(67). Several modifications have been suggested since that time to increase the reactivity of the metal. The majority of these modifications have employed zinc-copper couples(68-72), sodium-zinc alloys(73), or zinc-silver couples(77). Some recent work has indicated that certain zinc-copper couples will react with alkyl bromides to give modest yields of dialkylzinc compounds(74,73). However, all attempts to react zinc with aryl iodides or bromides have met with failure. The primary use of zinc couples has been in the Simmons-Smith reaction. This reaction has been primarily used with diiodomethane as 1,1-dibromides or longer chain diiodides have proven to be too unneactive even with the most reactive zinc couples. 

Reactions of 2 with alkyl halides were generally more successful for C-C bond formation. For example, bibenzyl was formed in good yield from the reaction of 2 with benzyl bromide. Dichlorodiphenylmethane and 1 reacted to give tetraphenylethylene in 63% yield. Similarly, diiodomethane reacted with 1 to give ethylene. This area of study is continuing. 

Another investigation180 181 can be taken as a lesson about the borderline in elucidating structures by comparison of experimental and calculated IR spectra. In the hope that dibromoformoxime may give carboxime (isofulminic acid) (135) (the only missing member in the series 132-135) upon irradiation in a similar manner to the dehalogenation of diiodomethane (see Section m.B.l), we carried out such an experiment. At first glance it looked as if the anticipated reaction had occurred.180 It needed a lot of effort to show that in reality the photochemistry of matrix-isolated dihaloformoximes is very complex.181... 

Among methods of preparing optically active cyclopropane compounds, the Simmons-Smith reaction, first reported in 1958, is of significance. This reaction refers to the cyclopropanation of alkene with a reagent prepared in situ from a zinc-copper alloy and diiodomethane. The reaction is stereospecific with respect to the geometry of the alkene and is generally free from side reactions in contrast to reactions involving free carbenes. 

A convenient method for the conversion of aldehydes (RCHO) to alkenes (RCH = CHj), knovm as methylenation, involves the reaction of a zinc/copper couple with diiodomethane in the presence of the carbonyl compound dissolved in tetrahy-drofuran. The reaction first generates an organometallic intermediate (ICH2ZnI) which then reacts with the carbonyl compound. The conversion of benzaldehyde to styrene using this conventional methodology required a reaction time of 6 h at 40 °C. When the reaction was sonicated however comparable yields of around 70%... 

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