Bicyclobutanes as unusual building blocks for complexity generation in organic synthesis

Communications Chemistry, Journal Year: 2023, Volume and Issue: 6(1)

Published: Jan. 12, 2023

Abstract Bicyclobutanes are among the most highly strained isolable organic compounds and their associated low activation barriers to reactivity make them intriguing building-blocks in chemistry. In recent years, numerous creative synthetic strategies exploiting heightened have been presented these discoveries often gone hand-in-hand with development of more practical routes for synthesis. Their proclivity as strain-release reagents through weak central C–C bond has harnessed a variety addition, rearrangement insertion reactions, providing rapid access rich tapestry complex molecular scaffolds. This review will provide an overview different options available bicyclobutane synthesis, main classes that can be prepared from bicyclobutanes, modes used.

Language: Английский

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Strain-Release Photocatalysis

Journal of the American Chemical Society, Journal Year: 2023, Volume and Issue: 145(38), P. 20716 - 20732

Published: Sept. 15, 2023

The concept of strain in organic compounds is as old modern chemistry and was initially introduced to justify the synthetic setbacks along synthesis small ring systems (pars construens strain). In last decades, chemists have developed an arsenal strain-release reactions destruens strain) which can generate─with significant driving force─rigid aliphatic that act three-dimensional alternatives (hetero)arenes. Photocatalysis added additional dimension processes by leveraging energy photons create chemical complexity under mild conditions. This perspective presents latest advancements photocatalysis─with emphases on mechanisms, catalytic cycles, current limitations─the unique architectures be produced, possible future directions.

Language: Английский

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Selective [2σ + 2σ] Cycloaddition Enabled by Boronyl Radical Catalysis: Synthesis of Highly Substituted Bicyclo[3.1.1]heptanes

Journal of the American Chemical Society, Journal Year: 2023, Volume and Issue: 145(7), P. 4304 - 4310

Published: Feb. 10, 2023

In contrast to the traditional and widely-used cycloaddition reactions involving at least a π bond component, [2σ + 2σ] radical between bicyclo[1.1.0]butanes (BCBs) cyclopropyl ketones has been developed provide modular, concise, atom-economical synthetic route substituted bicyclo[3.1.1]heptane (BCH) derivatives that are 3D bioisosteres of benzenes core skeleton number terpene natural products. The reaction was catalyzed by combination simple tetraalkoxydiboron(4) compound B2pin2 3-pentyl isonicotinate. broad substrate scope demonstrated synthesizing series new highly functionalized BCHs with up six substituents on 99% isolated yield. Computational mechanistic investigations supported pyridine-assisted boronyl catalytic cycle.

Language: Английский

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ortho-Selective Dearomative [2π + 2σ] Photocycloadditions of Bicyclic Aza-Arenes

Journal of the American Chemical Society, Journal Year: 2023, Volume and Issue: 145(22), P. 12324 - 12332

Published: May 26, 2023

Dearomative photocycloadditions are valuable chemical transformations, serving as an efficient platform to create three-dimensional molecular complexity. However, the photolability of original addition product especially within context ortho cycloadditions often causes undesired consecutive rearrangements, rendering these cycloadducts elusive. Herein, we report ortho-selective intermolecular photocycloaddition bicyclic aza-arenes including (iso)quinolines, quinazolines, and quinoxalines by utilizing a strain-release approach. With bicyclo[1.1.0]butanes coupling partners, this dearomative [2π + 2σ] cycloaddition enables straightforward construction C(sp3)-rich bicyclo[2.1.1]hexanes directly connected N-heteroarenes. Photophysical experiments DFT calculations revealed origin selectivity indicate that, in originally proposed energy transfer or direct excitation pathways, chain reaction mechanism is operative depending on conditions.

Language: Английский

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Dearomative ring expansion of thiophenes by bicyclobutane insertion

Science, Journal Year: 2023, Volume and Issue: 381(6653), P. 75 - 81

Published: July 6, 2023

Skeletal ring enlargement is gaining renewed interest in synthetic chemistry and has recently focused on insertion of one or two atoms. Strategies for heterocyclic expansion through small-ring remain elusive, although they would lead to the efficient formation bicyclic products. Here, we report a photoinduced dearomative thiophenes by bicyclo[1.1.0]butanes produce eight-membered rings under mild conditions. The value, broad functional-group compatibility, excellent chemo- regioselectivity were demonstrated scope evaluation product derivatization. Experimental computational studies point toward photoredox-induced radical pathway.

Language: Английский

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Pyridine-Boryl Radical-Catalyzed [2π + 2σ] Cycloaddition of Bicyclo[1.1.0]butanes with Alkenes

ACS Catalysis, Journal Year: 2023, Volume and Issue: 13(7), P. 5096 - 5103

Published: March 30, 2023

Bicyclo[2.1.1]hexanes (BCHs) represent an intriguing class of structurally rigid hydrocarbons that can serve as the bioisosteres benzenoids in medicinal chemistry. Methods for synthesis BCHs are, however, limiting. Reported herein is a facile via strain-release-driven [2π + 2σ] cycloaddition bicyclo[1.1.0]butanes (BCBs) with alkenes facilitated by pyridine-boryl radical catalyst. The mild reaction conditions, broad substrate scope, and decent functional group tolerance this protocol render it appealing relevant fields drug design synthesis. Theoretical mechanistic studies reveal relay mechanism involved. Synthetic applications products are performed.

Language: Английский

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Photocatalyzed [2σ + 2σ] and [2σ + 2π] Cycloadditions for the Synthesis of Bicyclo[3.1.1]heptanes and 5- or 6-Membered Carbocycles

Journal of the American Chemical Society, Journal Year: 2023, Volume and Issue: 145(46), P. 25411 - 25421

Published: Nov. 7, 2023

We report the use of photocatalysis for homolytic ring-opening carbonyl cyclopropanes. In contrast to previous studies, our approach does not require a metal cocatalyst or strong reductant. The cyclopropanes can be employed both [2σ + 2σ] and 2π] annulation with either alkenes/alkynes bicyclo[1.1.0]butanes, yielding cyclopent-anes/-enes bicyclo[3.1.1]heptanes (BCHs), respectively. BCHs are promising bioisosteres 1,2,4,5 tetra-substituted aromatic rings. Mechanistic including density functional theory computation trapping experiment DMPO, support 1,3-biradical generated from cyclopropane as key intermediate these transformations.

Language: Английский

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Intermolecular Formal Cycloaddition of Indoles with Bicyclo[1.1.0]butanes by Lewis Acid Catalysis

Angewandte Chemie International Edition, Journal Year: 2023, Volume and Issue: 62(48)

Published: Aug. 16, 2023

Abstract Herein, we develop a new approach to directly access architecturally complex polycyclic indolines from readily available indoles and bicyclo[1.1.0]butanes (BCBs) through formal cycloaddition promoted by commercially Lewis acids. The reaction proceeded stepwise pathway involving nucleophilic addition of BCBs followed an intramolecular Mannich form rigid indoline‐fused structures, which resemble indole alkaloids. This tolerated wide range BCBs, thereby allowing the one‐step construction various indoline polycycles containing up four contiguous quaternary carbon centers.

Language: Английский

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Silver‐Catalyzed Dearomative [2π+2σ] Cycloadditions of Indoles with Bicyclobutanes: Access to Indoline Fused Bicyclo[2.1.1]hexanes**

Angewandte Chemie International Edition, Journal Year: 2023, Volume and Issue: 62(48)

Published: Oct. 12, 2023

Bicyclo[2.1.1]hexanes (BCHs) are becoming ever more important in drug design and development as bridged scaffolds that provide underexplored chemical space, but difficult to access. Here a silver-catalyzed dearomative [2π+2σ] cycloaddition strategy for the synthesis of indoline fused BCHs from N-unprotected indoles bicyclobutane precursors is described. The strain-release operates under mild conditions, tolerating wide range functional groups. It capable forming with up four contiguous quaternary carbon centers, achieving yields 99 %. In addition, scale-up experiment synthetic transformations cycloadducts further highlighted utility.

Language: Английский

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General Synthesis of 3‐Azabicyclo[3.1.1]heptanes and Evaluation of Their Properties as Saturated Isosteres**

Angewandte Chemie International Edition, Journal Year: 2023, Volume and Issue: 62(39)

Published: May 26, 2023

Abstract A general approach to 3‐azabicyclo[3.1.1]heptanes by reduction of spirocyclic oxetanyl nitriles was developed. The mechanism, scope, and scalability this transformation were studied. core incorporated into the structure antihistamine drug Rupatidine instead pyridine ring, which led a dramatic improvement in physicochemical properties.

Language: Английский

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