Tandem Cross‐Dimerisation/Oxonia‐Cope Reaction of Carbonyl Compounds to Homoallylic Esters and Lactones

Abstract

Conceptually different: This allyltransfer reaction is catalyzed by Lewis acids (LAs) and proceeds atom‐economically by disproportionation of the carbonyl groups through organized oxonia‐Cope transition states (see scheme). A stereoselective [n+4] ring enlargement leads to a variety of macrolides with 9‐ to 16‐membered rings.

Palladium‐Catalyzed Stagewise Strain‐Release‐Driven C−C Activation of Bicyclo[1.1.1]pentanyl Alcohols

“…β,γ-Unsaturated ketones are also an important molecular scaffold in biologically active and natural compounds, [23] and serve as versatile intermediates in organic synthesis. [24] At the stage of condition optimization, it was found β,γ-enone product was obtained in 39 % yield, when using Pd(OAc) 2 as a catalyst (entry 11, Table 1). Thus, we were delighted to find that arylated (Z)-β,γ-enones were isolated by flash column chromatography as major products in moderate yields in toluene solvent (Scheme 4), which offered a new strategy to yield a range of γ-arylated β,γ-unsaturated ketones.…”

Catalytic Asymmetric Prins Bicyclization for the endo‐Selective Formation of 2,6‐dioxabicyclo[2.2.2]octanes

“…Various aliphatic and aromatic aldehydes reacted with substrate 6 a (R 1 , R 2 , R 3 , R 4 =CH 3 ; R 5 =H) to produce bicyclic acetals 7 b – j with good yield and excellent diastereoselectivity (>99:1). Formaldehyde, a notoriously difficult coupling partner in oxy‐oxonia‐Cope rearrangements,, generated dioxabiclooctane 7 b , albeit in lower yield. Different hydrocarbon substituents, ether or ester functionalities, as well as other less reactive double bonds were compatible with the reaction conditions yielding products 7 c – m .…”

Efficient Macrocyclization by a Novel Oxy‐Oxonia‐Cope Reaction: Synthesis and Olfactory Properties of New Macrocyclic Musks

“…The synthesis of further unsaturated macrocyclic musks can shed light upon similarities in the structure–odor correlation of these two musk families, and to this purpose we herein report on the intramolecular application of a new reaction6 of β,γ‐unsaturated aldehydes with different aldehydes in the presence of Lewis acids. The projected macrocyclization can be regarded as an oxy‐version of the established 2‐oxonia Cope rearrangement,7, 8 but as illustrated in Scheme , could as well proceed through compound 11 in a Prins‐type9, 10 manner by coordination of the Lewis acid to the opposite formyl function.…”