Abnormal Behaviour of Allenylsulfones under Lu’s Reaction Conditions: Synthesis of Enantiopure Polyfunctionalised Cyclopentenes

Abstract

Formal [3+2] cycloadditions of 5-alkoxyfuran-2(5H)-ones 1 and 2 with allenylsulfones 3-5, promoted by different nucleophiles, afford 3-alkoxy-5-arylsulfonyl-3,3 a,6,6 a-tetrahydro-1H-cyclopenta[c]furan-1-ones in good yields with complete control of both regio- and pi-facial selectivity. The incorporation of a sulfinyl group on the furanone ring enhances the reactivity of the furanones and allows the synthesis of optically pure, bicyclic adducts in good yields. Allenylsulfones evolve through a different mechanism to that proposed for allenoates (Lu's reaction) and afford bicyclic adducts in which the sulfonyl group is joined to C-5. This has advantages on the stereochemical control of further reactions leading to enantiomerically pure polyfunctionalised cyclopentenes and cyclopentanes.

Phosphine Organocatalysis

“…Although it did not employ chiral induction from an optically active phosphine catalyst, an asymmetric variant of Lu’s [3 + 2] annulation has been developed by Martín and Ruano using a chiral sulfinyl group as an auxiliary directing chiral induction (Scheme 241). 310,311 Excellent chiral induction was achieved in the synthesis of functionalized 5,5-fused bicyclic systems. In contrast to the asymmetric process, a stoichiometric amount of chiral auxiliary was required.…”

Facile synthesis of 4H-chromene derivatives via base-mediated annulation of ortho-hydroxychalcones and 2-bromoallyl sulfones

“…This is in sharp contrast with the widespread use of electronically similar allenyl esters (allenoates) in numerous useful reactions (see for examples [ 18 – 20 ]). The propensity of allenyl sulfones to oligomerise and display anomalous reactivity profiles in presence of base has, to some extent, dissuaded chemists from devising synthetic applications of allenyl sulfones [ 21 – 22 ]. We envisaged that such problems may be circumvented by developing a synthetic surrogate for the sensitive allenyl sulfones.…”

Unique Reactivity of α‐Substituted Electron‐Deficient Allenes using Sulfinate Salts as Lewis Base Organocatalysts

“…During this investigation, García Ruano extended also for the first time the annulation process to an α‐methyl allenyl sulfone [R 1 =Me, Eq. (2)] …”