Carbon configuration

In order to establish the bridgehead carbon configuration with certainty and to demonstrate the usefulness of the method, desilylation and deprotection of 438b in acidic conditions have been performed. Since they are accompanied by double bond migration and loss of chirality, a dimethylcuprate alkylation has been carried out before acid hydrolysis (Scheme 59) [112]. 

Rgem R(raM = substituents at the olefinic carbons (configuration relative to the carboxy group) ... 

All these cyclodehydration products are the result mainly of an inside chain oxygen attack on a primary carbon the chiral carbon configurations remain unchanged. The only exception to this rule concerns the secondary products obtained from glucitol. 

In very nearly all of its covalent compounds, carbon forms four bonds. The carbon atom (configuration is Is2 2s2 2p2), however, has only two unpaired electrons in its ground state and by a process of reasoning similar to that in the preceding paragraph, carbon would be expected to form only two covalent bonds. Confronted with this inconsistency, one is tempted to look for ways in which the carbon configuration can be modified to give four unpaired electrons. Suppose, for instance that the... 

When a bis-homoallylic amine containing a nucleophilic ester group 5 undergoes iodocycliza-tion, formation of a frara.v-2,5-disubstituted pyrrolidine ring is favored, followed by conversion of the iodoamine to an aziridine. The intramolecular capture of the intermediate aziridinium salt by participation of the proximate ester results in a net retention of carbon configuration and total stereoselectivity123. 

Distortions of sp Carbon Configuration. Flattened and Pyramidalized sp Carbon... 

TABLE 30. Energy difference (kcal moi carbon configuration s... 

Figure 11.22. Schematic sequence of diamond nucleation on an Si hillock (a) initially deposited carbon configuration, and H ion etching, (b) etching of Si surface and formation of tilted diamond nucleus, and (c) growth of the nucleus, and formation of a Si hillock due to H+ ion etching [308],...

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