Deuterated cyclopropanes

Rotations of more deuterated cyclopropanes can be found in Refs 72 and 73. 

When the bis-deuterated cyclopropane trans-178b-d2 was reacted with Na/K in THF at 0°C one observed on protonation after 1 h besides 16 % trans-178b-d2,6 % propene 179-dj and 78 % propane 181b-d2. 

Most alkyl carbanions undergo facile pyramidal inversion. Cyclopropyl anions are an exception, presumably because the transition state, with a planar trigonal carbon, is more strained than the ground state. The configurational stability of cyclopropyl anions is of value in the synthesis of deuterated cyclopropanes by the Haller-Bauer reaction (see Section II.B). An interesting dilemma arises when a cyclopropyl anion is stabilized by a n-electron acceptor substituent such as a nitrile or an ester. Will the anion then retain its pyramidal equilibrium geometry for the strain reasons alluded to above, or will it become planar in order to maximize overlap of the filled orbital on carbon with the n orbital of the substituent Walborsky and coworkers addressed this question in a series of experiments in which rates of H/D exchange and racemization were compared for an optically active cyclopropane exposed to a base in a deuterated hydroxylic solvent. The outcome can be illustrated with the particular example of 1,1-diphenylcyclopropane-2-... 

In a preliminary study, it was shown that the bromination of cyclopropane in the presenee of iron gives a mixture of bromination products 1-3. The main adducts were 1,2- (2) and 1,3-dibromopropane (3) with a ratio of 46 39 at a reaction temperature of — 15°C and 60 10 at 60 °C. In mechanistic studies, bromine underwent addition to deuterated cyclopropanes (lrans-cyclopropane-l,l,2,3-d4 and ds-cyclopropane-l,2,3-dj) and gave almost exclusively the meio-l,3-dibromopropane derivatives as the result of a primary attack of the bromo cation at the edge with retention and the secondary addition of the bromide to the four-membered bromonium ion with inversion of configuration. ... 

This copper catalyst was also used to prepare specifically deuterated cyclopropane derivatives in optically active form79-80. The cyclopropanation of a more complex olefin methyl (2 )-3-isopropyl-6-methyl-2,5-heptadienoate can be achieved with surprisingly high cc when ( —)-menthyl diazoacetate is employed in the presence of the S-catalyst82. In this case a detailed description of various reaction parameters on the ee has been presented82. 

Deuterated cyclopropane has been brominated with bromine in order to determine the mechanism of electrophilic halogenation. The observed stereochemistry indicates initial edge halogenation with retention to form a four-membered bromonium ion, followed by nucleophilic ring opening with inversion194 l95. 

Isomerisation of Deuterated Cyclopropanes—the Possibility for Stereochemical Control. 

The direction of ring opening by homolytic cleavage of a cyclopropane bond is controlled by the stability of the diradical species formed. Upon heating of the mono-deuterated vinylcyclopropane 3, a mixture of the two isomeric mono-deuterated cyclopentenes 4 and 5 is formed ... 

We have previously in a number of papers [1-5] investigated these effects ft -both the Jahn-Teller inactive molecule n-butane [1] and the Jahn-Teller active molecules ethane, cyclopropane, and cyclohexane [2-5]. The choice of systems was largely dictated by the availability of experimental results [5-8]. New experiments being performed on selectively deuterated benzene have motivated a closer theoretical study of this system, and a first presentation of these investigations is given in the present paper. 

Baldwin et al. have used the same catalyst/diazo ester combination for the synthesis of optically active deuterated phenylcyclopropanes (Scheme 28) 197). From cis-1,2-dideuteriostyrene, d/-menthyl a-deuteriodiazoacetate and (+)-195d, the cis- and mnw-cyclopropanes 196 were obtained, both with 90% optical purity. The dominant enantiomer of trans-196 had (+)-(15, IS, 35) configuration. Analogously, the cyclopropanes c -198 and trans-198, obtained from styrene, d/-menthyl a-deuteriodiazoacetate and (+)-195d with subsequent transesterification of cisjtrans-197, had optical purities of 86 and 89%, respectively. The major optical isomer of cis-198 had (IS, 2R) configuration, that of trans-198 (IS, 2S) configuration. 

The fact that Schrock s proposed metallocyclobutanes decomposed to propylene derivatives rather than cyclopropanes was fortunate in that further information resulted regarding the stereochemistry of the olefin reaction with the carbene carbon, as now the /3-carbon from the metal-locycle precursor retained its identity. The reaction course was consistent with nucleophilic attack of the carbene carbon on the complexed olefin, despite potential steric hindrance from the bulky carbene. Decomposition via pathways f-h in Eq. (26) was clearly confirmed in studies utilizing deuterated olefins (67). 

The mechanism of this unusual cis addition has not been clarified. The bromoethyl derivative 2 can be further alkylated (intramolecularly) to give the deuterated cyclopropyl derivative 3. Once again, cis addition predominates, with 46% de. Upon hydrolysis of the cyclopropyl derivative, optically active (V)-l-amino-cyclopropane-2-r/2-l-carboxylic acid (4) in 44% yield and 46% ee is obtained. 

Rotational Raman spectroscopy is a powerful tool to determine the structures of molecules. In particular, besides electron diffraction, it is the only method that can probe molecules that exhibit no electric dipole moment for which microwave or infrared data do not exist. Although rotational constants can be extracted from vibrational spectra via combination differences or by known correction factors of deuterated species the method is the only one that yields directly the rotational constant B0. However for cyclopropane, the rotational microwave spectrum, recording the weak AK=3 transitions could be measured by Brupacher [20],... 

Despite the low pressure, both, the cyclopropane and the cyclobutane signals fade due to collisional dephasing. The effect is stronger for the larger molecule cyclobutane. As a consequence, fewer recurrences could be recorded for C4H8 and the values obtained are less accurate. Investigations in molecular beams could circumvent this, but with the drawback that the temperature of the sample is not known. The accuracy of the constants in the limit of the approximation is obtained from extrapolating microwave data of deuterated species. In combination with molecular beam experiments the method will yield new and more accurate constants. 

The glyoxime-Co(II)-catalyzed asymmetric cyclopropanation shown in Scheme 94 is noteworthy (226). The results of the detailed kinetic study are consistent with the mechanism of Scheme 92, however, the intermediary Co carbenoid species has substantial radicaloid properties, and only styrene and other conjugated olefins can be used as substrates. Simple alkenes are not cyclopropanated by diazo compounds. The reaction of deuterated styrene proceeds in non-stereospecific manner without retention of geometrical integrity. 

The reaction of optically active (l-diethoxyphosphoryl)vinyl p-tolyl sulfoxide (20) with sulfur ylides has provided the corresponding cyclopropanes (21) in high yields (g) (Scheme 10).52,53 With fully deuterated dimethyl(oxo)sulfonium methylide, (CD3)2 S(0)CD2, the cyclopropanation reaction occurred in a highly diastereoselective... 

Cyclopropane. The absorption spectrum of cyclopropane consists of three continuous regions146 with maxima at 1202, 1449, and 1594 A. At 1470 A., the absorption coefficient is 260 15 atm.-1 cm.-1, while the corresponding value for the fully deuterated material is 206 20.114... 

We said that the formation of cyclopropanes by addition of substituted carbenes to alkenes was rare—in fact, alkyl-substituted carbenes undergo very few intermolecular reactions at all because they decompose very rapidly. When primary alkyl halides are treated with base, alkenes are formed by elimination. Having read Chapter 19, you should expect the mechanism of this elimination to be E2 and, if you started with a deuterated compound like this, the alkene product would be labelled with two deuterium atoms at its terminus. 

Protonated cyclopropanes have been extensively reviewed recently 28,29) and only the main conclusions and most important experimental data will be summarized here. The reader is referred to these reviews for greater detail. Baird and Abodeiin 20) showed that when cyclopropane is treated with 8.43 M D2SO4 the recovered cyclopropane was partially deuterated (Eq. (21)). In later work by these same authors i 7), by... 

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