Iterative Asymmetric Allylic Substitutions: syn‐ and anti‐1,2‐Diols through Catalyst Control

Abstract

Eine kupferkatalysierte asymmetrische allylische Boronierung (AAB) ermöglicht den Zugang zu syn‐ und anti‐1,2‐Diolen. Die Methode erleichtert eine iterative Strategie zur Synthese von Polyolen (siehe Schema), wie z. B. vollständig differenziertes L‐ribo‐Tetrol und geschütztes D‐arabino‐Tetrol. P=Schutzgruppe.

Cross‐Metathesis/Iridium(I)‐catalyzed Allylic Etherification Strategy: (Iterative) Catalytic Asymmetric Synthesis of syn‐ and anti‐1,2‐Diols

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1,2-Diol functional groups are common structures in many biologically active natural products [1] and "privileged" chiral catalysts/ligands. [9] Although highly selective formation of differentiated syn-and anti-1,2-diols could be achieved by using a pair of enantiomeric ligands, the strategy required two extra steps for the in situ oxidation of the boronate product of the AAB reaction and the subsequent alcohol protection, and the AAB reaction did not occur with a TBS protecting group, thus considerably limiting the generality and practicality of the strategy.In recent years, iridium(I)-catalyzed allylic substitution reactions have emerged as a powerful tool for the enantioselective introduction of carbon-carbon and carbon-heteroatom bonds. 1,2-Diols can appear in many different forms depending on their protection state (diprotected, monoprotected, or free diol), as well as their absolute and relative stereochemistry (syn or anti).

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“…To our knowledge, the only catalytic asymmetric method that met the above two criteria was recently reported by the McQuade group, who employed the copper-catalyzed asymmetric allylic boronation/cross-metathesis (AAB/CM) strategy. [9] Although highly selective formation of differentiated syn-and anti-1,2-diols could be achieved by using a pair of enantiomeric ligands, the strategy required two extra steps for the in situ oxidation of the boronate product of the AAB reaction and the subsequent alcohol protection, and the AAB reaction did not occur with a TBS protecting group, thus considerably limiting the generality and practicality of the strategy.In recent years, iridium(I)-catalyzed allylic substitution reactions have emerged as a powerful tool for the enantioselective introduction of carbon-carbon and carbon-heteroatom bonds. [10] A distinct feature of iridium(I)-catalyzed allylic substitution reactions is the formation of chiral branched allylation products from achiral linear allyl sub-strates, which complements the more traditional palladiumcatalyzed allylic substitution reactions which typically give rise to linear allylation products.…”

“…To our knowledge, the only catalytic asymmetric method that met the above two criteria was recently reported by the McQuade group, who employed the copper-catalyzed asymmetric allylic boronation/cross-metathesis (AAB/CM) strategy. [9] Although highly selective formation of differentiated syn-and anti-1,2-diols could be achieved by using a pair of enantiomeric ligands, the strategy required two extra steps for the in situ oxidation of the boronate product of the AAB reaction and the subsequent alcohol protection, and the AAB reaction did not occur with a TBS protecting group, thus considerably limiting the generality and practicality of the strategy.…”

Concise Synthesis of (S)-δ-CEHC, a Metabolite of Vitamin E

“…Compound 3 is commercially available or could be readily prepared from o -cresol through a chromatography-free procedure in three steps. 22 Chiral synthon 2 can be produced smoothly using a reported method in two steps with 98% ee starting from (−)-linalool, 23 an inexpensive and commercially available natural product.…”

Asymmetric Synthesis of Chiral 1,3‐Disubstituted Allylsilanes via Copper(I)‐Catalyzed 1,4‐Conjugate Silylation of α,β‐Unsaturated Sulfones and Subsequent Julia‐Kocienski Olefination

“…With NHC‐3 (McQuade's six‐membered NHC), [ 57‐60 ] the enantioselectivity was further increased to 26% ee but with decreased yield (entry 5). To our joy, the reaction with ent ‐NHC‐4, a newly prepared six‐membered NHC with bigger steric hindrance, provided 3a in 55% yield with significantly enhanced enantioselectivity (60% ee) (entry 6).…”