A Novel NO₂/OH Exchange in α‐Nitro Ketones: A mechanistic investigation

Abstract

The reaction of r-nitro ketones to the corresponding a-hydroxy ketones under basic aqueous conditions, a novcl tr;tnsforniation. was studied. The investigation revealed that the reaction is only possible with I-nitro kctotics that are CH-acidic in the %'-position and readily deprotonated under the reaction conditions. The N O 2 OH exchange was established to proceed with retention of configuration at the stereogenic center, and I.iheling expcriments have shown that the O H 0-atom originates. to a great extent, from the solvent. In particular, the \tercochemical course of the reaction and the incorporation of external nucleophiles led us to propose a mc.ch;inism that involves neighboring-group participation. The product formation is explained by a double S,2 1-caction. which proceeds virr a Fmor.skii-like cyclopropanone intermediate.

Effects of Single α-to-β Residue Replacements on Structure and Stability in a Small Protein: Insights from Quasiracemic Crystallization

“… However, for each of these three quasiracemates, the unit cell contains twice the number of VHP chains (eight vs four) and is approximately double the volume of the VHP racemate unit cell (Figure ). Comparable unit cell expansion has been observed for small molecule quasiracemates relative to the corresponding racemate and is characterized by translational noncrystallographic symmetry. − …”

The Favorskii Rearrangement: Synthetic Applications

“…The transformation of -nitro ketones to the corresponding -hydroxy ketones under basic aqueous conditions has been studied [77]. The NO 2 /OH exchange was only possible in -nitro ketones that are CH-acidic at the ' position.…”

Xialenons, New Pentalenons fromStreptomyces

“…5, 183.7, and 204.0) the 13 C-NMR spectrum points to an α,β-unsaturated carbonyl group. The assignment of the low-field signal δ ϭ 183.7 to a double bond carbon is justified by comparison to the chemical shift of the double bond carbon atoms in bicyclo [3.3.0]-1(5)-en-2-one [6] (δ ϭ 187.3 and 148.8), which bears a similar α,β-unsaturated carbonyl group. 1 H-1 H as well as 1 H-13 C correlated 2D NMR spectroscopy demonstrates the connective sequence of the following two segments: allyl group (δ ϭ 5.10/5.05, 5.81 and 2.57/ 2.14) Ϫ methine group (δ ϭ 3.30) Ϫ methine group (δ ϭ 4.49) as well as methine group (δ ϭ 5.01) Ϫ methylene group (δ ϭ 2.68/2.10) Ϫ methylene group (δ ϭ 2.49/2.34).…”