Copper‐Catalyzed Asymmetric Borylative Cyclization of Cyclohexadienone‐Containing 1,6‐Dienes

Abstract

Due to the low reactivity of 1,6‐dienes and the challenge of selectively differentiating such two olefins, the development of metal‐catalyzed asymmetric cyclization of 1,6‐dienes remains largely underdeveloped. Herein, we describe the first copper(I)‐catalyzed asymmetric borylative cyclization of cyclohexadienone‐tethered terminal alkenes (1,6‐dienes) via a tandem process: the regioselective borocupration of the electron‐rich terminal alkene and subsequent conjugate addition of stereospecific secondary alkyl‐copper(I) to the electron‐deficient cyclohexadienone, affording enantioenriched bicyclic skeletons bearing three contiguous stereocenters in all cis‐form. Meanwhile, this mild catalytic protocol is generally compatible with a wide range of functional groups, which allows further facile conversion of the cyclization products.

Transition‐Metal Catalyzed Stereoselective Desymmetrization of Prochiral Cyclohexadienones

“…However, trans-internal olefins gave the corresponding product 26.2 g, albeit in low yield and excellent enantioselectivity. Stereochemically, this work is in contrast with their previous work i. e. Cu-catalyzed borylative cyclization of cyclohexadienone-tethered terminal alkenes [16] gave consecutive stereocentres in cis-cis form.…”

“…Very recently, the same research group [16] developed unprecedented Cu-catalyzed tandem borylative cyclization of cyclohexadienone-tethered terminal alkenes to synthesize cishydrobenzofurans 10.2 in presence of (R,R)-QuinoxP ligand 10.L (Scheme 10). The substrate scope includes various alkyl, aryl, haloaryl, haloalkyl, alkyl esters, heterocyclic groups at the quaternary center gave moderate to good yield (44-89 %), moderate enantioselectivity (71-86 % ee), and high diastereoselectivity (> 20 : 1 dr).…”

Nickel‐Catalyzed Hydroborylative Polycyclization of Allenynes: an Atom‐Economical and Diastereoselective Synthesis of Bicyclic 5‐5 Fused Rings

“…Only two examples of borylative cyclization of diynes can be found in the literature, with Co and Cu. [19] Finally, examples of borylative cyclization of dienes with Rh [20] and Cu [21] have also been described.…”

One-Pot Preparation of Tricyclo[5.2.2.04,9]undecanes via Cu-Catalyzed Asymmetric Carboboration of Cyclohexadienone-Tethered Allenes

“…Recently, significant progress has been made in borylcopper (Cu–B)-catalyzed borylation of allenes, especially carboboration of allenes (Scheme a). − The reactions of Cu–B species with allenes result in useful β-borylated allylcopper intermediates, which subsequently undergo a variety of transformations with different carbon electrophiles: aldehydes, ketones, imines, and nitriles for 1,2-addition; allyl phosphates for boroallylation; aryl iodides for boroarylation; dienoates for 1,6-addition; formate esters, carboxylic anhydrides, and acyl fluorides for boroacylation; bromoalkynes for boroalkynylation; and alkyl halides for alkylboration . Despite the above notable advances, the 1,4-addition of β-borylated allylcopper especially to α,β-unsaturated ketones has never been uncovered, due to the fact that the six-membered chairlike transition state makes the 1,2-addition to ketone more favorable . Herein, we present Cu-catalyzed asymmetric carboboration of cyclohexadienone-tethered allenes, which involves asymmetric 1,4-addition of β-borylated allylcopper to enone, thereby establishing a one-pot preparation of highly enantioenriched tricyclo­[5.2.2.0 4,9 ]­undecanes via the aforementioned carboboration and subsequent tandem oxidation/intramolecular aldol reaction (Scheme b).…”