In Situ Formation of Allyl Ketones via Hiyama−Nozaki Reactions Followed by a Chromium-Mediated Oppenauer Oxidation

• Published in: Journal of organic chemistry Vol. 67; no. 7; pp. 1975 - 1981
• Main Authors: Schrekker, Henri S, de Bolster, Martin W. G, Orru, Romano V. A, Wessjohann, Ludger A
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 05.04.2002; Amer Chemical Soc
• Subjects: Chemical reactivity; Chemistry; Chemistry, Organic; Exact sciences and technology; Organic chemistry; Physical Sciences; Reactivity and mechanisms; Science & Technology; REDUCTIONS; HALIDES; BETA,GAMMA-UNSATURATED KETONES; REAGENTS; HOMOALLYL ALCOHOLS; CHROMIUM(II)-MEDIATED REFORMATSKY REACTIONS; CARBOXYLIC ESTERS; ALDEHYDES; INDUCTION; Process conditions; Substituent effect; Chromium II Chlorides; Benzaldehyde; Oppenauer oxidation; Bromine Organic compounds; Aldehyde; Chemical synthesis; Ketone; Allylic compound
• ISSN: 0022-3263; 1520-6904
• DOI: 10.1021/jo001750u

In Hiyama−Nozaki reactions of allylchromium with aldehydes the expected products are homoallylalcohols. However, oxidation products derived from these, predominantly allyl ketones, can be common side products. This can be explained by an Oppenauer−(Meerwein−Ponndorf−Verley)-type mechanism (OMPV-reaction). The amount of oxidation is strongly dependent on the substitution pattern of the reaction partners and the reaction conditions. An appropriate choice of these can lead to preferential formation of ketones instead of the alcohols. In addition to its synthetic usefulness, the oxidation−reduction equilibrium is of the utmost importance for the design of enantioselective Hiyama−Nozaki reactions because it is also a potential racemization pathway.