Visible Light-Induced Reactions of Diazo Compounds and Their Precursors

Abstract

In recent years, visible light-induced reactions of diazo compounds have attracted increasing attention in organic synthesis, leading to improvement of existing reactions, as well as to the discovery of unprecedented transformations. Thus, photochemical or photocatalytic generation of both carbenes and radicals provide milder tools toward these key intermediates for many valuable transformations. However, the vast majority of the transformations represent new reactivity modes of diazo compounds, which are achieved by the photochemical decomposition of diazo compounds and photoredox catalysis. In particular, the use of a redox-active photocatalysts opens the avenue to a plethora of radical reactions. The application of these methods to diazo compounds led to discovery of transformations inaccessible by the classical reactivity associated with carbenes and metal carbenes. In most cases, diazo compounds act as radical sources but can also serve as radical acceptors. Importantly, the described processes operate under mild, practical conditions. This Review describes this subfield of diazo compound chemistry, particularly focusing on recent advancements.

Scheme 1.

Diazo Compounds under Visible Light Irradiation

Scheme 2.

Diverse Transformations of Singlet Carbenes

Scheme 3.

Wolff Rearrangement and Its Applications

Scheme 4.

Synthesis of β-Lactams via Wolff Rearrangement

Scheme 5.

Chiral Phosphoric Acid-Catalyzed Enantioselective Synthesis of Chiral Amides via Wolff Rearrangement

Scheme 6.

Esterification via Wolff Rearrangement

Scheme 7.

Regioselective Acylation of β-Ketoesters with α-Diazo Ketones

Scheme 8.

Isocyanides as C-Nucleophiles

Scheme 9.

Synthesis of Dicarbonyl Sulfoxonium Ylides

Scheme 10.

Pd-Catalyzed Asymmetric Formal [4 + 2] and [5 + 2] Cycloadditions

Scheme 11.

Pd-Catalyzed Formal [3 + 2] Cycloaddition Employing Vinyl Cyclopropanes

Scheme 12.

Asymmetric Formal [4 + 2] Cycloaddition via Organocatalysis

Scheme 13.

Photochemical Formal [2 + 2] and [3 + 2] Cycloaddition

Scheme 14.

Intermolecular Cyclopropanation of Diazo Compounds with Alkenes and Arenes

Scheme 15.

Intramolecular Cyclopropanation of Diazo Compounds with N-Protected Indoles

Scheme 16.

One-Pot Cyclopropanation and Transesterification Approach Toward Cyclopropane-Fused Lactones

Scheme 17.

Cyclopropenation of Diazo Compounds with Alkynes

Scheme 18.

Cyclopropenation of Diaryl Diazo Compounds with Alkynes

Scheme 19.

Intermolecular C–H Insertions of Diazo Compounds

Scheme 20.

Intramolecular C–H Insertions of Diazo Compounds

Scheme 21.

Intermolecular C–H Insertions of Diaryl Diazo Compounds with Terminal Alkynes

Scheme 22.

C–H Insertions of Aryl Redox-Active Diazo Compounds

Scheme 23.

B–H Insertions of Diazo Compounds with NHC Boranes

Scheme 24.

N–H Insertions of Diazo Compounds

Scheme 25.

Enantioselective N–H Insertion Catalyzed by Chiral Phosphoric Acid

Scheme 26.

Enantioselective N–H Insertion Catalyzed by Chiral Phosphamide

Scheme 27.

O–H Insertions of Diazo Compounds

Scheme 28.

Si–H Insertions of Diazo Compounds

Scheme 29.

S–H Insertions of Diazo Compounds

Scheme 30.

Formation of Ylides

Scheme 31.

[2,3]-Sigmatropic Rearrangement of Ammonium Ylides

Scheme 32.

Formal [4 + 1]-Annulation of Diazoacetates with o-Aminoacetophenones

Scheme 33.

Divergent Synthesis of Aziridines and Imidazolidines

Scheme 34.

Synthesis of Amide from Diazo Compounds and Nitrosoarenes

Scheme 35.

Formation of Nitrile and Pyridinium Ylides

Scheme 36.

Ring Expansion and Contraction of Oxonium Ylides

Scheme 37.

Photochemical Cascade Ring-Opening Reactions of Oxonium Ylides

Scheme 38.

NHC-Catalyzed Approach for Synthesis of O-Protected Hydroxylamines

Scheme 39.

Cascade Ring-Opening Reactions of Oxonium Ylides Using Acceptor-Type Diazo Compounds

Scheme 40.

Synthesis of Ketones from Nitroso Arenes

Scheme 41.

Synthesis of Propargylic Esters via Oxonium Ylide Intermediates

Scheme 42.

[2,3]-Sigmatropic Rearrangement of Sulfonium Ylides

Scheme 43.

Sommelet–Hauser and [1,2]-Rearrangement of Sulfonium Ylides

Scheme 44.

Ring Expansion of Sulfonium Ylides

Scheme 45.

Synthesis of 3-Arylidene Oxindoles

Scheme 46.

Copper-Catalyzed Asymmetric Formal [4 + 1] Cycloadditions

Scheme 47.

Selective Visible Light Photolysis of Donor–Acceptor Diazoalkanes in the Presence of Acceptor-Type Diazo Compound

Scheme 48.

Synthesis of Thiazolines from α-Diazo 1,3-Diketones and β-Ketothiamides

Scheme 49.

Arylation and Alkylation of Diazo Compounds with Boronic Acids

Scheme 50.

Site-Selective N¹-Alkylation of N-heterocycles with α-Diazoacetates

Scheme 51.

Synthesis of Imines and Sulfoxonium Ylides Using Diazo Compounds

Scheme 52.

Racemic Approach for Formal C–C Bond Insertion

Scheme 53.

Asymmetric Formal C–C Bond Insertion Using Chiral Phosphoric Acid Catalysts

Scheme 54.

Asymmetric Formal C–C and C–H Bond Insertion Using Chiral Guanidine Amide Catalysts

Scheme 55.

Synthesis of Ketenimines and Tetrasubstituted Alkenes

Scheme 56.

Free Carbenes as Hydride Acceptor

Scheme 57.

Trifluoromethylsulfonylation Reaction of Aryl Diazoesters Enabled by Manganese Catalysis

Scheme 58.

Pd-Catalyzed C–H Alkylation of 1-Naphthylamines with α-Diazoester

Scheme 59.

1,2-Rearrangement of Alkyl Redox-Active Diazo Compounds

Scheme 60.

Spin State of Bis(4-methoxyphenyl)carbene

Scheme 61.

Generation of Triplet Carbene via Energy Transfer

Scheme 62.

Reaction of Aryl–Aryl Diazo Compounds with Terminal Alkynes via Triplet Carbene Intermediates

Scheme 63.

Photocatalytic gem-Difluoroalkenylation, Stereoconvergent Cyclopropanation Reactions and C3-Alkylation of Indoles by Diazo Acetates via Triplet Carbene Intermediates

Scheme 64.

Triplet Carbene as an HAT Reagent

Scheme 65.

Generation of Alkyl Radicals from Diazo Compounds via Cobalt Catalysis

Scheme 66.

Generation of Alkyl Radicals from Diazo Compounds via PCET

Scheme 67.

Heck Reaction of Diazo Compounds via Photoinduced Palladium Catalysis

Scheme 68.

Photocatalytic 1,2-Amino-alkylation of Styrenes with Diazoacetates and Diarylamines

Scheme 69.

Difunctionalization of Alkenes via Cooperative Photoredox and NHC Catalysis

Scheme 70.

Photocatalytic 1,2-Oxo-Alkylation of Styrenes with Diazoacetates and Hydroperoxides

Scheme 71.

Photocatalytic Minisci Reactions

Scheme 72.

Photocatalytic Difunctionalization of Alkenes with Diazo Compounds and tert-Butyl Nitrite

Scheme 73.

Photocatalytic Alkylation of Pyrroles and Indoles with α-Diazo Esters

Scheme 74.

Photocatalytic Transformations Involving Radical–Radical Recombinations

Scheme 75.

Asymmetric Alkylation with Diazo Compounds

Scheme 76.

Visible Light-Induced Benzannulation Reaction of Diazo Ketones and Alkynes

Scheme 77.

Organophotocatalytic Approach for Synthesis of Phenanthridines

Scheme 78.

Synthesis of α-Fluorovinylphosphonates

Scheme 79.

Synthesis of Disubstituted Bicyclo[1.1.1]pentanes

Scheme 80.

Generating Diazomethyl Radicals via Photoredox Catalysis

Scheme 81.

Photocatalytic Synthesis of Acridines

Scheme 82.

Synthesis of Oxadiazoles via Diazomethyl Radical Intermediates

Scheme 83.

Synthesis of N-Amino Triazoles from α-Diazo Sulfonium Triflates

Scheme 84.

Synthesis of Triazole Derivatives from Hypervalent Iodine Reagents

Scheme 85.

Synthesis of Oxadiazoles and Pyrazoles from α-Diazo Sulfonium Triflates

Scheme 86.

Photocatalytic Method for Accessing Oxalate Esters from Diazo Compounds and α-Bromo-ketones

Scheme 87.

Synthesis of N-Alkyl Hydrazones

Scheme 88.

Synthesis of 4-Fluoroacridines via Cascade Radical Cyclization

Scheme 89.

1,3-Functionalization of Vinyl and Alkynyl Diazo Compounds

Scheme 90.

Photochemical Synthesis of Dihydrotriazole from Diazo Compounds, Azodicarboxylates, and Nitriles

Scheme 91.

Synthesis of Fluorinated N-Heterocycles via Multicomponent Cyclization Reactions

Scheme 92.

Nucleophilic Sites in Diazo Compounds

Scheme 93.

Organic Dye-Catalyzed Coupling Reaction Between Tertiary Amines and Diazo Compounds

Scheme 94.

Synthesis of Aziridines via Organophotoredox Catalysis

Scheme 95.

Radical Cation Cyclopropanations via Chromium Photooxidative Catalysis

Scheme 96.

Formal [3 + 2] Cycloadditions of Vinyl Diazo Compounds with Alkenes or Indoles

Scheme 97.

Regioselective C–H Alkylation of Arenes Enabled by Organic Photoredox Catalysis

Scheme 98.

Photocatalytic Self-Cyclization of Vinyldiazo Compounds

Scheme 99.

Iodine-Enabled Diazo Activation to Access Radical Reactivity

Scheme 100.

Photoexcited Proton Transfer Reaction

Scheme 101.

Synthesis of α-Ketoesters via Aerobic Oxidation of α-Diazoesters

Scheme 102.

Generation of Free Carbyne Radical Intermediates from α-Diazo Sulfonium Triflates

Scheme 103.

Solvent-Dependent Selectivity of Cyclic Diazo Imides

Scheme 104.

In Situ Formation of Diazo Compounds from N-Tosylhydrazones

Scheme 105.

Photochemical Generation of Carbenes from N-Tosylhydrazones

Scheme 106.

Denitrogenative Sulfonylation of N-Sulfonylhydrazones

Scheme 107.

Heck Reaction of N-Tosylhydrazones via Photoinduced Palladium Catalysis

Scheme 108.

Synthesis of Ketones and Aldehydes Enabled by Photoexcitation of N-Tosylhydrazone Anions

Scheme 109.

Synthesis of Tetrasubstituted Cyclopropanes Enabled by Energy Transfer

Scheme 110.

[3 + 2] Cycloaddition of in Situ Formed Diazo Compounds and Alkenes

Scheme 111.

Light-Induced and Metal-Free Transformations of Pyridotriazoles

Scheme 112.

Cyclopropanation of Oxadiazolines

Scheme 113.

In Situ Formation of Diazo Species from (β-Amino-α,α-difluoroethyl)phosphonates