Platinum(II)-Catalyzed Asymmetric Ring-Opening Addition of Arylboronic Acids to Oxabenzonorbornadienes

Abstract

A new platinum(II)-catalyzed asymmetric ring-opening addition of arylboronic acids to oxabenzonorbornadienes was developed, which afforded the corresponding cis-2-aryl-1,2-dihydronaphthalen-1-ol products in high yields (up to 97%) with moderate to good enantioselectivities (up to 89% ee) under very mild conditions. The effects of various ligands, catalyst loading, bases, solvents, and temperatures on the yield and enantioselectivity of the reaction were also investigated. The cis configuration of product 2m was confirmed by X-ray diffraction analysis. A potential mechanism for the present catalytic reaction is proposed.

Chiral Palladacycle Catalysts Generated on a Single‐Handed Helical Polymer Skeleton for Asymmetric Arylative Ring Opening of 1,4‐Epoxy‐1,4‐dihydronaphthalene

“…The ee value of the product was improved (94 %) by lowering the reaction temperature to 0 °C (entry 3). This result indicates that the PQXphos‐based chiral palladacycle acts as an efficient catalyst in the ring‐opening desymmetrization of 1 a with phenylboronic acids and has higher enantioselectivity than the palladacycle catalyst system developed by Hou and co‐workers (79 % ee ),8c the platinum catalyst system developed by Yang and co‐workers (84 % ee ),8e and the rhodium catalyst system developed by Lautens et al. (92 % ee ) 8a.…”

“…In the case of 4‐ or 3‐substituted phenylboronic acids, both electron‐donating and electron‐withdrawing groups led to products with high enantioselectivities (entries 1–6). The use of 2‐substituted phenylboronic acids 2 h and 2 i afforded products with slightly decreased enantioselectivities (entries 7 and 8), although the selectivities were much higher than those obtained using a low‐molecular‐weight palladacycle ( 3 ah , 30 % ee )8c and platinum catalysts ( 3 ah , 11 % ee; 3 ai , 49 % ee ) 8e. Derivatives of 1,4‐epoxy‐1,4‐dihydronaphthalene bearing substituents at the 6,7‐positions were applicable for the reaction (entries 9 and 10), although the presence of 5,8‐dimethoxy groups lowered the reactivity and led to product with moderate enantioselectivity (entry 11).…”

Palladium/Zinc Co‐Catalyzed syn‐Stereoselectively Asymmetric Ring‐Opening Reaction of Oxabenzonorbornadienes with Phenols

“…With the aid of various chiral transition‐metal catalysts, a variety of carbo‐2–6 and heteroatom nucleophiles7–11 reacted with oxabenzonorbornadienes successfully leading to substituted hydroxyl‐dihydronaphthalenes. In the ring‐opening addition of carbonucleophiles to oxabenzonorbornadienes, both cis and trans configured products can be obtained in a highly diastereoselective and enantioselective manners by choosing different metal catalysts, such as Rh,6b, 12 Cu,2e, 3a, b Pd,2a, b, f, 6c, 13 Pt14 and Ni 15. Yet, for the ring‐opening addition of oxabenzonorbornadienes with oxygen‐ or nitrogen‐based nucleophiles, only trans ‐configuration products were generally observed with Rh, Ir or Ru catalysts 7.…”

Boron Reagents and Catalysts for the Functionalization of Strained Heterocycles

“…Their asymmetric ring opening by arylboronic acids has attracted considerable attention as it offers a straightforward access to chiral aryltetralins, which are common substructures in bioactive natural products (Scheme 15). After seminal work by Lautens and co‐workers using rhodium in combination with ferrocenylphosphine catalysts, [56] other metal‐catalyzed procedures for the asymmetric arylative ring opening of oxabenzonorbornadienes with arylboronic acids emerged in the more recent literature [57,58] …”