Prochiral carbonyl groups

At the very start of Chapter 17, we introduced stereochemistry by thinking about the reactions of two sorts of carbonyl compounds. They are shown again here the first has a prochiral carbonyl group. The second, on the other hand, is not prochiral because no stereo genic centre is created when the compound reacts. 

Exactly the same things are true for the faces of a prochiral carbonyl group or double bond. 

For the syn substrate 8, the approach of the organometallic nucleophile is controlled by the steric bias imposed by the bulky DiTOX ring (Fig. 2). The nucleophile approaches the prochiral carbonyl group from the direction of the... 

Prochiral carbonyl groups and alkenes can show different facial reactivity, exemplified, respectively, by enzymic reduction of... 

The Felkin-Anh Model [CP2, G5, M5, N2, N5, NNl, WHl, WH2, WP2, WTl] The attack of a hydride H on a prochiral carbonyl group can be accomplished either on the Re or Si face of the carbonyl, leading to a pair of diastereomers, as shown in the models in Figure 3.10. In these models L represents the most bulky group, P the most polar, and S the smallest group. Initially Cram [CA2] proposed model 3.18 to interpret the formation of the major isomer. This is called Cram in Figure 3.10, and the other isomer is labeled anti-Cram. ... 

In the organosilicon substrates 213b, 215b, 217 and 219, the prochiral carbonyl groups reduced by the microorganisms are attached to two carbon atoms and are relatively far... 

A weaker, intramolecular version of the n k interaction between a lone pair and a carbonyl group has been implicated in structural changes associated with pyramidalization of carbonyl groups in peptides. Raines and coworkers used crystallographic analysis to demonstrate that such interactions can induce chirality in an otherwise planar, prochiral carbonyl group (Figure 2.49). ... 

It was originally proposed that in the absence of a chelating metal counterion, conformation (9) would be favoured owing to the electronic repulsion of the oxygen atoms [7]. Intermolecular hydride delivery would then be favoured from the least sterically hindered face of the prochiral carbonyl group. 

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