Michael Additions in Aqueous Media: “On‐Water” and “In‐Water” Processes from α‐Nitro Ketones and Their Anions

Abstract

A variety of α,β‐unsaturated aldehydes and ketones gave very high‐yielding Michael addition reactions with α‐nitrocycloalkanones in water, at room temperature without added catalyst. These can be considered as one of the very few “on‐water” Michael reactions known in the literature, because they took place in suspension or emulsion and at increased speed relative to the same transformations performed in organic solvents. A related protocol that uses very dilute, aqueous solutions of potassium carbonate as the reaction media extended the scope of the method to cyclic enones and unsaturated esters, nitriles and sulfones and is likely to take place in the bulk of the aqueous phase, i.e., “in‐water”. Both preparative methods constitute environmentally benign and efficient alternatives to previously known procedures.

Palladium-Catalyzed (Z)-Selective Allylation of Nitroalkanes: Access to Highly Functionalized Homoallylic Scaffolds

“…Finally, when benzoyl nitromethane was employed, we observed a postsynthetic shift of the phenyl ketone group to the alcohol unit, resulting in the formation of the phenyl ester-based allylated nitroalkane 3q isolated in 67% yield . The assigned stereochemistry of all products was fully consistent with their 2D NMR data (see 1 H– 1 H NOESY NMR for 3d ; Supporting Information), and in the case of 3o , it was further confirmed by X-ray diffraction (see inset in Scheme and Supporting Information).…”

New Degradation Pathways of the Key Aroma Compound 1-Penten-3-one during Storage of Not-from-Concentrate Orange Juice

“…With 3 and 4 as reference compounds, peak B in the stored aqueous solution of 1-penten-3-one was characterized as 4 , which is a side-product of the cyclic Diels–Alder product formed by hydration under aqueous conditions at elevated temperatures …”

“…Retention Indices and Mass Fragments (MS-EI) for Two Degradation Products Formed from 1-Penten-3-one (1) (Figure 4) formed by hydration under aqueous conditions at elevated temperatures. 22 To find out whether the degradation products of 1 are present in a food, the volatile fractions isolated from fresh and 8 months stored orange juice were screened for 2 and 4 by means of GC × GC-TOF/MS. While 2 was found in all juice samples, 4 was not detectable.…”

High-yielding aqueous synthesis of chloroacetophenones and aroyl chlorohydrins

“…Therefore, various methods have been developed to reduce the amount of volatile organic solvents such as solvent-free mechanical chemical conversions, [1][2][3][4][5][6][7] deep eutectic solvent-mediated reactions, 8 ionic liquid-mediated reactions [9][10][11][12][13] and aqueous reactions. [14][15][16][17][18][19][20][21][22] Our group has developed several types of aqueous reactions, [23][24][25][26] some of which perform even better than the conventional organic solventmediated reactions. For example, when organic solvents were replaced with water in aqueous Darzens reactions between haloketones and aldehydes, a quantitative yield of the pure product was obtained aer a simple ltration workup (i.e.…”