Cyclopropyl bromide, reaction

First, the extent of solvent attack in cyclopropyl bromide reactions is quantitatively consistent with the D model (Figure 7.25) [52,971. 

Alkylation of cyclopropyl bromides. - Reaction of a bromocyclopropane with this cuprate (4 -5 equiv.) in THF at — 48 to 0° and then with an alkyl bromide (or iodide) at the same temperature results in stereospecific replacement of the bromo group by the alkyl group with retention of configuration. A mixed cuprate such as a is postulated as an intermediate. An example is the conversion of rra y-l-bromo-... 

The reaction of cyclopropyl bromide with triphenylphosphine gives the expected phosphonium salt in less than 1 % yield. An alternate route to the salt by the thermal decomposition of 2-oxo-3-tetrahydrofuranyltriphenylphosphonium bromide gives a... 

Among transition metal complexes, the ubiquitous dicarbonylcyclopentadienyliron (Fp) complexes are the first, and perhaps the best, representatives to demonstrate the utility of metal-halogen exchange reactions in metallacyclopropane synthesis. Thus, reaction of the readily available sodium dicarbonylcyclopentadienyliron [Cp(CO)2Fe]Na (FpNa) with the parent cyclopropyl bromide " and derivatives " gave in moderate yields the corresponding cyclopropane-Fp complexes (equation 3). 

Cyclopropanecarboxylic acids can be converted into cyclopropyl bromides by the Hunsdiecker reaction " . The reaction of cyclopropyl bromides with K3Co(CN)5 produces non-stereospecifically the corresponding cyano derivatives " gem-Dibromocyclopro-panes also afford directly the cyano- and acetoxycyclopropanes upon treatments with K3Co(CN)5 and Cu(OAc)2, respectively " Trimethylsilylcyclopropane provides cyclopropyl ketones by the Friedel-Crafts reaction ". ... 

In more recent work, Leandri and coworkers have solvolysed a series of methylene dialkyl and methylene spiro cyclopropyl bromides as a method for preparing a-allenic tertiary alcohols. An example is shown below in the reaction of 1. Robertson and... 

The formation of cyclopropyl halide radical anion pairs as intermediates is also invoked in Sr I type substitution reactions by Rossi and Meijs . It seems that the photostimulated reaction of cyclopropyl bromides like 7-bromonorcarane (120) with Ph2P M to give 121 involves a radical chain, and halogen-containing radical anions as chain carrier. 

The reaction of hot tritium atoms with cyclopropyl bromide... 

Davanloo and Wai studied the reaction of hot tritium from the He(n, p)T reaction with gaseous cyclopropyl bromide. Table 6 gives the ratio of the yields in the presence of I2 as a scavenger. Due to the low vapor pressure of c-CjHsBr at room temperature, the effect of stabilization was observed by the addition of CHjBr. It acts both as a stabilizer and as a moderator, thus reducing the yields of all hot products, and the important results are the ratios of the yields of the various organic products. 

This step cannot be followed up since it does not lead to radioactive organic products. However, the fact that the sum of CH2=CHCH Br and CHf Br is almost independent of the pressure indicates that this last step is of small imprortance in the case of Br + cyclopropane. This step, however, is important in the case of Br-I-cyclopropyl bromide. For Br -f cyclopropyl bromide Saeki and Tachikawa found that the increase of total pressure led also to a decrease in the yield of tHf Br and increase in the yield of CH2 =CHCH Br. However, while the yield of CH Br decreased from 3.1 % to 2.1 % (when the pressure was changed from 1.37 to 13.4 kPa), the yield of CH2=CHCH2Br increased from 3.0 to 12.3%. The difference between the decomposition of c-CaHf Br formed by either Br for H reaction or Br for Br reaction was explained by Saeki and Tachikawa as due to the higher energy (above 4 eV) left in the molecule in the Br-for-H reaction which... 

The effect of the electron scavenger, CS2, is explained as due to preventing the neutralization of the cations in the system and subsequent reaction of in the state with cyclopropane or with the radiolytic products of the substrate. In the presence of CS2 the major product is methyl iodide similarly to the major product of Br found by De Jong and coworkers . However the analog to the main product in the case of I2 or O2 as scavenger, namely, n-propyl bromide was not found at all by De Jong and co workers. They found the second and third major products to be allyl bromide and cyclopropyl bromide while Certout and Schleifer did not find the respective iodides at all. It is not clear if this is due to the difference between Br and I or due to the different amount of radiolysis induced by each of them. 

As in the previously investigated Grignard reaction of cyclopropyl bromide [70], the exocyclic cyclopropyl olefin 18 could not be isolated from the reaction mixture. Since it was suspected that olefin 18 would not be stable under the Grignard reaction conditions, an authentic sample was synthesized in 60% yield by zinc-induced elimination of the tosylate precursor in DMF. The Grignard reaction of 13 was repeated in the presence of this olefin and under the same conditions (1 hr at room temperature). The olefin 18 was shown to undergo complete polymerization. 

The most general entry into functionalized sulfur-containing cyclopropanes is the addition reactions of cyclopropanones and thiols (see Section 5.2.3.5.4.). Thus, reaction of cyclo-propanone with thiols in dichloromethane affords l-(alkylsulfanyl)cyclopropanols 39 which are readily transformed into the corresponding cyclopropyl bromides 40 and cyclopropyl chlorides 41 upon reaction with anhydrous hydrogen bromide and hydrogen chloride, respectively. ... 

Fig. 7.24. Yields of products of reactions of magnesium with cyclopropyl bromide (Cplirl in diethyl ether iSII) at 37"C as a function of the initial concentrations of magnesium bromide ( MgBr. a) and cyclo-propyl bromide ( CpBr]n). Symbols as lor Figure 7.2.1. The curves represent the yields when MgBr, (, = 0 and are taken from Figure 7.23 MgBr n =0.18 M. MgBr ](i = 2.6 M. Reprinted lioui (iarst <-/ /. 98. Copyright IW-4. Page No. 370. with permission from Elsevier Science.

Fig. 7.25. Ohsctved s calculated yields for Grignard reactions o cyclopropyl bromide in Did containing polar solutes at 37 C. The calculations use V = 2.5F and A = 2.71 1102. Calculated values of (CpCp). (SSt. and (CpS) include radical disproportionation product and arc consequently loo large. The calculated value ol (Cplll is for solvent attack only (docs net inctmk disproportionation) and is consequently too small.

Desorption and solvent attack are even dearer lor reactions ol Mg turnings with 2.2.3.3-tetra-inelliylcyclopropyl bromide in DEE. which are interesting lor other reasons as well 98. This bulky substrate does not react when stirred for an hour in DEE alone. However, in 2.6-.M MgBr>/ DEFi a smooth reaction begins immediate]). It is distinctly slower than reactions of typical alkyl bromides or of cyclopropyl bromide itself. 

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