Regiocontrolled Annulation of Benzocyclobutenols with Alkynes

Zeng, Qin-Qiong; Wang, Yongqi; Cheng, Lang; Wang, Bi‐Qin; Hu, Ping; Song, Feijie

doi:10.1021/acs.orglett.2c01023

Cited by 8 publications

(4 citation statements)

References 63 publications

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“…Then we first studied the transition-metal-catalyzed intramolecular transformation of O -bearing alkyne-tethered benzocyclobutenols 35 . The reaction was realized by using 1.0 mol % [Rh(OH)(cod)] 2 as a catalyst, 0.5 equiv of ZnCl 2 as a Lewis acid, and n PrOH as a solvent at 80 °C (Figure a) . Mechanistically, the reaction proceeds through β-carbon elimination of rhodium alcoholates IM22 resulting from the substitution of benzocyclobutenols 35 with a rhodium catalyst.…”

Section: C–c Bond Activation Of Strained-ring Compoundsmentioning

confidence: 99%

Transition-Metal-Catalyzed C–C Bond Formation from C–C Activation

Song,

Wang,

Shi

2023

Acc. Chem. Res.

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Ni-catalyzed cross coupling of aryl nitriles with arylboronic esters through C−CN cleavage. Encouraged by these results, we are interested in transition-metal-catalyzed C−C bond activation. Due to their broad availability, we then turned our attention to C−C cleavage of carboxylic acids. Rhodiumcatalyzed decarbonylative coupling of carboxylic acids with (hetero)arenes was then achieved through oxidative addition of in situ formed, more reactive mixed anhydrides to Rh(I) without the need for oxidants that are commonly required for the decarboxylative coupling of carboxylic acids. Subsequently, the decarbonylation of more challenging unstrained aryl ketones was realized under Rh catalysis assisted by N-containing directing groups. Following this work, a group exchange of aryl ketones with carboxylic acids was achieved through 2-fold C−C bond cleavage. By employing the chelation strategy, Rh-catalyzed C−C bond activation of secondary benzyl alcohols was also accomplished through β-carbon elimination of the rhodium alcoholate intermediates. The competing oxidation of secondary alcohols to ketones via β-hydrogen elimination of the same intermediates was suppressed as thermodynamically favorable five-membered rhodacycles are formed after β-carbon elimination. Different types of transformations of alcohols, including the Heck-type reaction with alkenes, cross coupling with arylsilanes, and Grignard-type addition with aldehydes or imines, have been achieved, showing the great potential of secondary alcohols in the formation of C−C bonds. These C−C bond-forming reactions are complementary to traditional cross couplings of aryl halides with organometallic reagents. However, these transformations produce small molecules as byproducts. To improve the atom economy, we then investigated C−C bond transformations of strained-ring cyclic compounds. Ni-catalyzed intermolecular cyclization of benzocyclobutenones with alkynes was recently achieved via the uncommon cleavage of the C1−C8 bond by employing a removable blocking strategy. Rhcatalyzed intramolecular annulation of benzocyclobutenols with alkynes was also achieved. In summary, our developments demonstrate the great potential of transition-metal-catalyzed C−C bond activation for the formation of new C−C bonds. To further expand the synthetic utility of C−C bond activation, more efforts are required to expand the substrate scope and to achieve earthabundant metal-catalyzed transformations.

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Section: C–c Bond Activation Of Strained-ring Compoundsmentioning

confidence: 99%

Transition-Metal-Catalyzed C–C Bond Formation from C–C Activation

Song,

Wang,

Shi

2023

Acc. Chem. Res.

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“…Following our continuous interests in the transition-metal-catalyzed intramolecular transformations of benzocyclobutenols for construction of benzo-fused ring systems, an unprecedented Rh-catalyzed intramolecular hydroarylation of benzocyclobutenols with unactivated alkenes is herein reported, which provides an alternative approach to 3,3-disubstituted 2,3-dihydrobenzofurans bearing a β-keto moiety at the 4-position under mild conditions (Scheme d). Notably, such kind of molecules is difficult to synthesize by the C–H activation strategy due to the weak directing ability of the β-carbonyl group.…”

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Rh-Catalyzed Intramolecular Hydroarylation of Unactivated Alkenes via C–C Bond Activation

Cheng

Dai

et al. 2023

ACS Catal.

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The transition-metal-catalyzed intramolecular hydroarylation of alkenes has been recognized as a straightforward approach for the construction of 3,3-disubstituted 2,3-dihydrobenzofurans. The reactions mainly rely on the reductive Heck reaction of aryl halides or the direct C−H bond activation of arenes bearing a directing group. This work realizes the Rh-catalyzed intramolecular hydroarylation of olefin-tethered benzocyclobutenols via C−C bond activation, which offers an alternative approach to 3,3-disubstituted 2,3-dihydrobenzofurans bearing a 4-β-keto moiety. The methodology features 100% atom economy and pH-and redox-neutral conditions, and is applicable to the late-stage functionalization of complex molecules. The asymmetric variant has also been achieved with excellent enantioselectivities.

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“…Dong and co-workers used the “cut-and-sew” strategy, which involved metal-catalyzed C–C bond functionalization by oxidative addition and coupling with unsaturated reagents . As a direct derivative of benzocyclobutanone, benzocyclobutenol also reacted in high activity and regioselectivity in intermolecular reactions via selective cleavage of the C(sp 2 )–C(sp 3 ) bond. − To date, metal-catalyzed C–C activation of benzocyclobutanols has been carried out in three reaction modes (Scheme ). First, the Orellana group reported Pd-catalyzed regioselective C(sp 2 )–C(sp 2 ) coupling of benzocyclobutenols with aryl bromides (Scheme a-1) .…”

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“…Second, Murakami et al pioneered the Rh(I)-catalyzed C–C activation of benzocyclobutenols en route to intermolecular [4 + 2] annulation with various π-bonds, which affords six-membered ring alcohol (Scheme a-2) . Since then, extensive studies on C1–C2 cleavage of benzocyclobutenols has been realized by Rh(I) catalysis, and annulation reactions with alkene, alkyne, allene, and isocyanate have been disclosed. This type of coupling has also been extended to intramolecular systems by taking advantage of the resulting ketone moiety.…”

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Cobalt/Rhodium-Catalyzed Diversified Amidation of Benzocyclobutenols via C–C Cleavage under Catalyst and Condition Control

et al. 2023

Org. Lett.

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Cobalt(III) and rhodium(III)-catalyzed regio- and chemoselective amidation of benzocyclobutenols has been realized using dioxazolone as the amidating reagent to afford three classes of C–N-coupled products via β-carbon elimination of the benzocyclobutenol. The Co(III)-catalyzed coupling initially afforded an isolable o-(N-acylamino)arylmethyl ketone, which could further cyclize to the corresponding indole derivatives under condition control. In contrast, efficient stepwise diamidation has been achieved under Rh(III) catalyst control. The chemoselectivities are jointly controlled by the catalyst and reactions conditions.

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Regiocontrolled Annulation of Benzocyclobutenols with Alkynes

Cited by 8 publications

References 63 publications

Transition-Metal-Catalyzed C–C Bond Formation from C–C Activation

Transition-Metal-Catalyzed C–C Bond Formation from C–C Activation

Rh-Catalyzed Intramolecular Hydroarylation of Unactivated Alkenes via C–C Bond Activation

Cobalt/Rhodium-Catalyzed Diversified Amidation of Benzocyclobutenols via C–C Cleavage under Catalyst and Condition Control

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