Oxidation of natural targets by dioxiranes. 2. Direct hydroxylation at the side chain C-25 of cholestane derivatives and of vitamin D3 Windaus-Grundmann ketone

If CH Bonds Could Talk: Selective CH Bond Oxidation

“…Consequently, many landmark discoveries in the field of C À H oxidation are not discussed, but hopefully the perspective taken herein will allow C À H oxidation reactions to be more readily incorporated into synthetic planning. electronically dissimilar tertiary sites can also be seen in 9, [16,17] but it should be stated that the difference in steric environment may also contribute synergistically to the observed selectivity in this case.…”

Continued Progress towards Efficient Functionalization of Natural and Non‐natural Targets under Mild Conditions: Oxygenation by C−H Bond Activation with Dioxirane

“…[45] In 2002, Breslow and co-workers developed ab iomimetic catalystf or steroids CÀHo xidation by using am anganese perfluoroporphyrin decorated with ac yclodextrin group. [46] In this context,d ioxirane 1a and 1b have successfully been employed in different synthetic procedures [5] and/ori nt otal synthesis to obtain site-selective hydroxylation of natural targets such as steroids, [47] vitamin D 3 derivatives, [48] and terpenes, [49] without the need for elaborate procedures. [14] Furthermore, the site-selective hydroxylation of target substratesb yd ioxirane are often used fori ntroduction of an oxidized functionality late in as ynthetic sequence (late-stage CÀH bond oxidation strategy) in total synthesis of natural products.…”

“…[1] Selected examples of natural productst hat utilize direct functionalization of CÀHb onda sak ey step are shown in Figure 3. [47,[50][51][52][53][54][55][56] Indeed, the CÀHb ond functionalization can be used as ak ey step to assemble complex moleculara rchitectures, although such as trategy can be complicated by selectivity issues in the functionalization step and in the increasing complexity of the substrates. [1,49] An umber of strategies have involved the use of electronic, steric, and stereoelectronic differences between aliphatic CÀHb onds in complex molecule settings,w hich are susceptible to site-selective oxidations.…”

Wenn C‐H‐Bindungen sprechen könnten – selektive Oxidationen von C‐H‐Bindungen

“…Gleiches gilt für 7 und 8, die beide zwei tertiäre Positionen haben, von denen die entferntere bevorzugt oxidiert wird. [13][14][15] Eine Unterscheidung zwischen zwei elektronisch verschiedenen tertiären Positionen kann auch in 9 beobachtet werden; [16,17] hier könnte allerdings auch die unterschiedliche sterische Umgebung synergistisch zur Selektivität beitragen.…”