From Olefins to Ketones via a 2‐Rhodaoxetane Complex

Abstract

Die quantitative Oxygenierung von 1,5‐Cyclooctadien zu 4‐Cyclooctenon mit molekularem Sauerstoff verläuft über ein 2‐Rhoda(III)‐oxetan (siehe Schema), das durch eine β‐Eliminierung das ungesättigte Keton leicht und selektiv freisetzt. Das Epoxid wird nicht gebildet.

Nickel‐Catalyzed Cross‐Coupling of Styrenyl Epoxides with Boronic Acids

“…Observation of α‐substituted alcohols as the major products in these reactions can be explained by initial oxidative addition to access metallaoxetane 1 17, 18 or its ring‐opened form, followed by β‐hydride elimination and reinsertion to afford η 2 ‐oxanickellacycle 2 (Scheme ) 19. Kulasegaram and Kulawiec20a,b have disclosed studies on palladium‐catalyzed epoxide isomerization that lend support to this proposal 20c–e. 21 Subsequent nickel‐catalyzed 1,2‐arylation with boronic acids, a transformation demonstrated recently by the research groups of Itami and Aoyama,22a,b would deliver the observed product 22c–g.…”

Rhodium Mediated CH Bond Functionalisation Leading to Carboxylate Derivatives

“…The way in which 2 is eliminated upon exposure of 1 to CO should be similar to that in previously reported reactions of complex 1 with phosphanes. [10] The second organic compound produced by the reaction (35 % yield) was identified as cycloocta-2,6-diene carboxylic acid 4 (see the Experimental Section). As the most relevant resonance, the proton from the À COOH moiety, unobserved at room temperature, was located as a sharp singlet (d = 13.67 ppm) at À70 8C in [D 8 ]toluene, whereas the carboxylic carbon appeared at the usual chemical shift (d = 180.7 ppm) in the 13 C{ 1 H} attached proton test (APT) spectrum.…”