Steric and Stereoelectronic Effects in Organic Chemistry by Veejendra K. Yadav

By Veejendra K. Yadav

The steric and stereoelectronic results regulate the speed and stereochemical consequence of reactions. therefore, an honest figuring out of the comparable suggestions is vital for winning man made making plans. The ebook makes an attempt to handle numerous vital matters with regards to those suggestions in a simplified demeanour, and is meant for graduate scholars. It lays rigidity at the vital facets of steric and stereoelectronic results and their keep watch over at the conformational profile and reactivity good points. The publication covers the geometrical requisites for reactions at saturated and unsaturated carbons in either cyclic and acyclic structures, and the consequent stereochemical positive factors. The element of geometrical flexibility can also be coated with a couple of examples regarding intramolecular reactions. It offers with the facial selectivity of nucleophilic additions to acyclic and cyclic carbonyl compounds, and explains how the steric and stereoelectronic results keep watch over a similar. The paintings reviews on allylic traces and their stereochemical regulate on diverse reactions with the comparable conformational keep an eye on. it's a needs to learn to appreciate the regulate parts, the trendy between those parts are spiro-conjugation, periselectivity, torquoselectivity, a-effect, Hammett’s substituent constants, Hammond postulate, and Curtin-Hammett precept.

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That the hydrolysis does not proceed via the pathway 92a ! 94 is conclusively demonstrated by the observation that such a pathway for the orthoester 106a (an equivalent of the conformer 92a) is likely to lead to both the ethyl and methyl esters as shown in the Eq. 30. Cleavage of the ring oxygen, after due protonation (not shown), under stereoelectronic control will generate 111. Hydration of 111 under the same two stereoelectronic effects that allowed a smooth cleavage of the ring rC–O bond will lead to 112a, which will be expected to exist in equilibrium with the conformer 112b.

Note that the anti relationship of the methyl substituent on the cyclobutane ring and the shown hydrogen on the cyclopropane ring is retained in the product olefin. Compare this with a similar cleavage of 222 that leads to 224 with Z-double bond, Eq. 65 [33]. Fragmentations of 219 and 222 proceed through stereoelectronically favored cleavages of the intermediates 220 and 223, respectively. Also note that the antiperiplanar relationship between rC1–C2 and rC3–C4 and also between rC1–C2 and the two electron pair orbitals, one on each of the two oxygen atoms on C1, allow the smooth cleavage.

Note that in the general transformation 61a ! 62, the group R1 that migrates from the oxygen-bearing carbon to the carbon bearing the leaving group Y is disposed in an anti relationship with both rC–X and electron pair orbital on the oxygen atom. If for some reason, steric or otherwise, the molecule adopts the conformation as in 61b, it is R2 that will migrate and yield the isomeric compound 63. Finally, the conformer 61c, wherein rC–O is anti to the leaving group Y, will lead to the epoxide 64.

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