Cyclopropane alkanal

The C6 thiourea 24 has been shown recently to be well suited for the enanti-oselective aza-Henry reaction of nitromethane with kettmines, yielding the products in high yields and ee s (Scheme 6.29) [71]. The reaction was also performed with a nitro-cyclopropane alkane and a trifluoromethyl substituted ketamine, thus forming a precursor for the synthesis of possible anti-HIV drug candidates. 

NBS can also be used to brominate alkanes. For example, cyclopropane, cyclopentane, and cyclohexane give the corresponding bromides when irradiated in a solution of NBS in dichloromethane. Under these conditions, the succinimidyl radical appears to be involved as the hydrogen-abstracting intermediate ... 

To name an alkane in which the carbon atoms form a single chain, we combine a prefix denoting the number of carbon atoms with the suffix -ane (Table 18.1). For example, CH,—CH, (more simply, CH,CH,) is ethane and CH,—CH2—CH, (that is, CH,CH2CH,) is propane. Cyclopropane, C,H6 (15), and cyclohexane, C6H12 (16), are cycloalkanes, alkanes that contain rings of carbon atoms. 

The present procedure for ring expansion has also been applied to l,2-bis(trimethylsilyloxy)bicyclo[n.l.0]alkanes, which are prepared by cyclopropanation of l,2-bis(silyloxy)cycloalkenes. The latter are readily available from acyloin condensations in the presence of chlorotrimethylsilane. " This reaction provides a new route to cyclic 1,3-diketones and macrocyclic compounds containing two 1,3-diketone units in the ring. 

C09-0122. Cyclopropane, C3 Hg, which has three carbon atoms in a ring, is far more reactive than other alkanes. 

The simplest of the saturated cyclic hydrocarbons, or cycloalkanes, is cyclopropane, C3Hg, the molecules of which are made up of three carbon atoms to each of which two hydrogen atoms are attached. Cyclopropane is somewhat more reactive than the corresponding open-chain alkane, propane, C3Hg. Other cycloalkanes make up a part of ordinary gasoline. 

The noteworthy point is a shortening of C-C bond distance as compared to the aliphatic C-C bond distance which is 1.54 A. This shortening manifests itself in the development of special character of the bonds. Since the sp orbitals of carbon now cannot overlap as effectively as they do in alkanes where perfect end-on overlap occurs the bonds in cyclopropane becomes bent and weak and also lead to an angle strain and so the molecule has greater potential energy. So this bent or banana bond accounts for the most of the ring strain. 

As previously mentioned, Davis (8) has shown that in model dehydrocyclization reactions with a dual function catalyst and an n-octane feedstock, isomerization of the hydrocarbon to 2-and 3-methylheptane is faster than the dehydrocyclization reaction. Although competitive isomerization of an alkane feedstock is commonly observed in model studies using monofunctional (Pt) catalysts, some of the alkanes produced can be rationalized as products of the hydrogenolysis of substituted cyclopentanes, which in turn can be formed on platinum surfaces via free radical-like mechanisms. However, the 2- and 3-methylheptane isomers (out of a total of 18 possible C8Hi8 isomers) observed with dual function catalysts are those expected from the rearrangement of n-octane via carbocation intermediates. Such acid-catalyzed isomerizations are widely acknowledged to occur via a protonated cyclopropane structure (25, 28), in this case one derived from the 2-octyl cation, which can then be the precursor... 

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