Diastereocontrol of [4 + 3] Cyclic Oxyallyl Cycloadditions by Alkoxy Substituents

8‐Oxabicyclo[3.2.1]oct‐6‐en‐3‐ones: Application to the Asymmetric Synthesis of Polyoxygenated Building Blocks

“…Cha and co‐workers effected the diastereoselective cycloaddition of a chiral α‐substituted α‐chlorocyclohexanone to furan (Scheme ) 32. Cycloaddition of chloroketone 28 with furan under dehydrohalogenation conditions provided 11‐oxatricyclo[4.3.1.1 2,5 ]undec‐3‐en‐10‐one 30 in 77 % yield and greater than 90 % ee .…”

A Semi-Pinacol Rearrangement Approach to Bicyclo[3.2.1]octan-2-ones and Bicyclo[3.2.1]octan-3-ones

“…Our approach was guided by continuing interest in utilizing 1,2-alkyl shift of epoxy alcohols and derivatives, which was pioneered by Tsuchihashi and Suzuki, 6,7 in nat-ural product synthesis. 8 As part of our investigation of asymmetric [4+3] cycloaddition, 9 the semi-pinacol rearrangement of 2,3-epoxy silyl ethers was envisioned to trigger ring expansion of bicyclo[2.2.1]heptan-2-ones so as to provide new access to the [4+3] cycloadducts such as the bicyclo[3.2.1]octanone system. Enantioselective epoxidation reactions of olefins, namely the Jacobsen and Shi epoxidations, 10,11 as well as the Sharpless asymmetric epoxidation of allylic alcohols, can be relied on to prepare the requisite substrates with high diastereoselectivity.…”

Syntheses and Applications of Functionalized Bicyclo[3.2.1]octanes: Thirteen Years of Progress

“…82 The latter compounds have 84 Also, Cha and co-workers developed a highly diastereoselective version of the reaction using cyclic oxyallyl cations bearing a β-alkoxy substituent such as 152, leading to 153. 85 In this version of the reaction, the face differentiation of the oxyallylic cation is attributed either to intramolecular hydrogen bonding in the cation resulting in a rigidification of its structure or simply to dipole repulsion in the cation resulting in a preferred conformation of it. This [4 + 3]-cycloaddition reaction has found an application in the straightforward synthesis of sodorifen (155a), a permethylated volatile, naturally occurring compound isolated from Serratia odorifera exhibiting a unique carbon skeleton as reported recently by Francke and co-workers.…”