Configurational structure, aliphatic

AH for this reaction we take to be 3.65 v.e., the energy required to break a C — C bond in aliphatic compounds. The second step of the dissociation consists in a change in the structure of the radicals, involving a change in nuclear configuration from a tetrahedral arrangement of... 

Seebach and Brenner have found that titanium enolates of acyl-oxazolidinones are added to aliphatic and aromatic nitroalkenes in high diastereoselectivity and in good yield. The effect of bases on diastereoselectivity is shown in Eq. 4.59. Hydrogenation of the nitro products yields y-lactams, which can be transformed into y-amino acids. The configuration of the products is assigned by comparison with literature data or X-ray crystal-structure analysis. 

A new amorphous alkaloid has been recently isolated from the Chinese plant T. bufalina (Ervatamia hainanensis) collected on Hainan Island (53). Its mass spectrum showed a molecular ion at m/z 382, corresponding to C23H30N2O3. From the fragmentation pattern, this compound would appear to be a coronaridine derivative in which a C2H50 unit is attached to the aliphatic moiety of the molecule. The structure 111 with (S) configuration at C-3 was determined by a detailed analysis of its H-NMR spectrum (Table IV) in comparison with the data of other ibogan alkaloids. 

The dipole moments and structures of the org azides and aliphatic diazo compds were studied by Sidgwick et al (Ref 4). Sheinker Syrkin (Ref 13) made vibrational spectra measurements of org azides and deduced the configuration of azide compds. UV spectra confirmed the observations made on Raman and IR spectra. Heats of combustion and formation of org azides were detd by Murrin Carpenter (Ref 16). Patterson et al (Ref 7) discussed the CA method of naming and indexing org azides. For addnl info and discussion of org azides see the general references (Refs 1,2,3,5,8,10 A 12)... 

Individual functional groups attached to a partially or fully reduced pyran ring behave much as expected of their aliphatic equivalents but there is often a quantitative difference in their reactivity which enables selective reactions to be carried out on polysubstituted compounds. Many examples of this are known in the tocopherol series which are the most important members of the chroman family. Since they are known by trivial names, these are shown with their structures (674). The most important tocopherol is natural vitamin E or a-tocopherol the four natural tocopherols have 7 -configuration at each of their asymmetric centres at C-2, C-4 and C-8. ... 

The aldimine of Figure 13.34 is a chiral and enantiomerically pure aldehydrazone C. This hydrazone is obtained by condensation of the aldehyde to be alkylated, and an enantiomerically pure hydrazine A, the S-proline derivative iS-aminoprolinol methyl ether (SAMP). The hydrazone C derived from aldehyde A is called the SAMP hydrazone, and the entire reaction sequence of Figure 13.34 is the Enders SAMP alkylation. The reaction of the aldehydrazone C with LDA results in the chemoselective formation of an azaenolate D, as in the case of the analogous aldimine A of Figure 13.33. The C=C double bond of the azaenolate D is fraws-configured. This selectivity is reminiscent of the -preference in the deprotonation of sterically unhindered aliphatic ketones to ketone enolates and, in fact, the origin is the same both deprotonations occur via six-membered ring transition states with chair conformations. The transition state structure with the least steric interactions is preferred in both cases. It is the one that features the C atom in the /3-position of the C,H acid in the pseudo-equatorial orientation. 

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