Science of Synthesis

Science of Synthesis is the authoritative and comprehensive reference work for the entire field of organic and organometallic synthesis.

Science of Synthesis presents the important synthetic methods for all classes of compounds and includes:

Methods critically evaluated by leading scientists

Background information and detailed experimental procedures

Schemes and tables which illustrate the reaction scope

Preface

As our understanding of the natural world increases, we begin to understand complex phenomena at molecular levels. This level of understanding allows for the design of molecular entities for functions ranging from material science to biology. Such design requires synthesis and, as the structures increase in complexity as a necessity for specificity, puts increasing demands on the level of sophistication of the synthetic methods. Such needs stimulate the improvement of existing methods and, more importantly, the development of new methods. As scientists confront the synthetic problems posed by the molecular targets, they require access to a source of reliable synthetic information. Thus, the need for a new, comprehensive, and critical treatment of synthetic chemistry has become apparent. To meet this challenge, an entirely new edition of the esteemed reference work Houben–Weyl Methods of Organic Chemistry will be published starting in the year 2000.

To reflect the new broader need and focus, this new edition has a new title, Science of Synthesis, Houben–Weyl Methods of Molecular Transformations. Science of Synthesis will benefit from more than 90 years of experience and will continue the tradition of excellence in publishing synthetic chemistry reference works. Science of Synthesis will be a balanced and critical reference work produced by the collaborative efforts of chemists, from both industry and academia, selected by the editorial board. All published results from journals, books, and patent literature from the early 1800s until the year of publication will be considered by our authors, who are among the leading experts in their field. The 48 volumes of Science of Synthesis will provide chemists with the most reliable methods to solve their synthesis problems. Science of Synthesis will be updated periodically and will become a prime source of information for chemists in the 21st century.

Science of Synthesis will be organized in a logical hierarchical system based on the target molecule to be synthesized. The critical coverage of methods will be supported by information intended to help the user choose the most suitable method for their application, thus providing a strong foundation from which to develop a successful synthetic route. Within each category of product, illuminating background information such as history, nomenclature, structure, stability, reactivity, properties, safety, and environmental aspects will be discussed along with a detailed selection of reliable methods. Each method and variation will be accompanied by reaction schemes, tables of examples, experimental procedures, and a background discussion of the scope and limitations of the reaction described.

The policy of the editorial board is to make Science of Synthesis the ultimate tool for the synthetic chemist in the 21st century.

We would like to thank all of our authors for submitting contributions of such outstanding quality, and, also for the dedication and commitment they have shown throughout the entire editorial process.

The Editorial Board

October 2000

D. Bellus (Basel, Switzerland)

S. V. Ley (Cambridge, UK)

R. Noyori (Nagoya, Japan)

M. Regitz (Kaiserslautern, Germany)

P. J. Reider (New Jersey, USA)

E. Schaumann (Clausthal-Zellerfeld, Germany)

I. Shinkai (Tsukuba, Japan)

E. J. Thomas (Manchester, UK)

B. M. Trost (Stanford, USA)

Volume Editor's Preface

This volume covers the synthesis of three- and four-membered heterocycles with maximum unsaturation and of five-membered hetarenes with one oxygen, sulfur, selenium, tellurium, nitrogen, or phosphorus atom. Maximum unsaturation means that the ring doesn't contain either a sp³-hybridized carbon atom or a heteroatom incapable of π-conjugation. Some compounds which are derivatives of such ring systems but no longer feature maximum unsaturation are also included, namely thiirene 1,1-dioxides, thiophene 1,1-dioxides, and λ⁵-phosphirenes or η¹-metal complexes of λ³-phosphirenes.

This volume deviates from the common principle of the series to treat benzo-annulated systems directly after the monocyclic ring systems. While this rule is observed where relevant for the three- and four-membered ring systems, annulated systems such as benzofurans, benzothiophenes, benzopyrroles (indoles) etc. are covered separately in Volume 10 (Fused Five-Membered Hetarenes with One Heteroatom). This was done because the three- and four-membered ring systems alone would not have filled one volume, and the material for monocyclic and benzo-annulated five-membered hetarenes is much too abundant for one volume.

The ring systems covered in this volume occupy a wide range of stabilities and reactivities. They can have a fleeting existence such as the antiaromatic three-membered rings of oxirene, thiirene, selenirene, and 1H-azirine, be highly reactive such as the kinetically stabilized, formally antiaromatic tri-tert-butylazete, or represent basic chemicals in their parent form, such as furan, pyrrole, and thiophene, which are tolerant to a broad range of reaction conditions during their synthesis and selective transformation. Also, the various ring systems described in this volume were introduced to the field of chemical science at well-spaced intervals over the last 200 years. While furans (2-furoic acid discovered by C. W. Scheele in 1780, correct ring structure proposed by A. von Baeyer in 1877), pyrroles (first detected by F. F. Runge in 1833, isolated purely in 1857, correct ring structure proposed in 1870), and thiophenes (discovered in 1882 by V. Meyer) have a rich history of well over one hundred years, the phospholes, congeners of the former, did not appear before 1959. Thiirenes, oxirenes, and 1H-azirines were closely studied as reactive intermediates and, in some cases, as matrix-isolated species mainly in the 1970s, azacyclobutadienes (azetes) appeared in 1973 and were a hot research topic in the 1980s, and many of the phosphorus-containing three- and four-membered heterocycles mentioned in this volume were reported over the last twenty years. Since the chemistry of the five-membered hetarenes furan, pyrrole, and thiophene had the longest time to mature, it is clear that the chapters on these three classes of ring systems are by far the largest ones in this volume.

The syntheses of furans, pyrroles, and thiophenes were discussed in Houben–Weyl, Vol. E 6. Since only six years have elapsed between the appearance of this publication and the present volume, the current authors were able to profit from the comprehensive and authoritative reviews in this Houben–Weyl volume and could critically evaluate the information given there and refer to it in Science of Synthesis (Volume 9). This Science of Synthesis volume is of course updated with the latest developments in the synthesis of these three important classes of hetarenes. It was certainly not easy for the authors of these three chapters to develop their own style of presenting the facts in light of the excellent contributions produced by the Houben–Weyl authors previously. Readers who notice that in some cases, the same experimental procedures have been selected in both the Houben–Weyl and Science of Synthesis volumes are assured that this was done deliberately with the explicit approval of the publishing house: It is self-evident that a specific method to construct a target molecule should be illustrated by a representative, well worked-out synthetic procedure, and no reason was seen to challenge the expertise of the former authors in the selection of suitable procedures.

This volume is only the second one in the new series Science of Synthesis. Since not only the concept but also the organizational scheme is different in some aspects from the former Houben–Weyl, the authors of the present volume did not have a model to follow in the formal presentation of their contributions. Furthermore, in the exactly three years between the start of this project and the publication, the organizational scheme for the volumes on hetarenes as well as the guidelines for authors have been refined constantly, not at least due to the continuous feedback between authors, volume editor, and editorial office. I am very grateful to all authors for their active participation in the development of our common project. I appreciate also their willingness to accept suggestions for changes that were given by me or the editorial office.

It is my great pleasure to thank the publishing house and the staff of the editorial office in Stuttgart for the smooth cooperation in this project. My particular thanks go to Dr. M. Fiona Shortt and to Lindsey Sturdy who were always open for discussions, ready to settle problems, and determined to move the project ahead.

Volume Editor

Ulm, November 2000

Gerhard Maas

Volume 9: Fully Unsaturated Small-Ring Heterocycles and Monocyclic Five-Membered Hetarenes with One Heteroatom

Preface

Volume Editor's Preface

Table of Contents

Introduction

G. Maas

9.1 Product Class 1: Oxirenes

K.-P. Zeller

9.2 Product Class 2: Thiirenes and Their Derivatives

N. Tokitoh and W. Ando

9.3 Product Class 3: Selenirenes

N. Tokitoh and W. Ando

9.4 Product Class 4: Tellurirenes

N. Tokitoh and W. Ando

9.5 Product Class 5: 1H-Azirines

K.-P. Zeller

9.6 Product Class 6: Phosphirenes

H. Heydt

9.7 Product Class 7: Three-Membered Rings with Phosphorus and One or More Heteroatoms

H. Heydt

9.8 Product Class 8: Four-Membered Rings with One or More Heteroatoms

M. Regitz and U. Bergsträßer

9.9 Product Class 9: Furans

B. König

9.10 Product Class 10: Thiophenes, Thiophene 1,1-Dioxides, and Thiophene 1-Oxides

J. Schatz

9.11 Product Class 11: Selenophenes

J. Schatz

9.12 Product Class 12: Tellurophenes

J. Schatz

9.13 Product Class 13: 1H-Pyrroles

D. StC. Black

9.14 Product Class 14: Phospholes

F. Mathey

Keyword Index

Author Index

Abbreviations

Table of Contents

Introduction

G. Maas

Introduction

9.1 Product Class 1: Oxirenes

K.-P. Zeller

9.1 Product Class 1: Oxirenes

9.1.1 Synthesis by Ring-Closure Reactions

9.1.1.1 By Formation of Two O—C Bonds

9.1.1.1.1 Fragments C—C and O

9.1.1.1.1.1 Method 1: Oxidation of Alkynes

9.1.1.1.1.1.1 Variation 1: With Peroxy Acids

9.1.1.1.1.1.2 Variation 2: With Dioxiranes

9.1.1.1.1.1.3 Variation 3: With Atomic and Molecular Oxygen

9.1.1.1.1.1.4 Variation 4: Enzymatic Oxidation

9.1.1.2 By Formation of One O—C Bond

9.1.1.2.1 Fragment O—C—C

9.1.1.2.1.1 Method 1: Isomerization of α-Oxo Carbenes

9.1.1.2.1.2 Method 2: Isomerization of Ketene

9.1.2 Synthesis by Ring Transformation

9.1.2.1 Method 1: From Larger Heterocycles by Extrusion Reactions

9.1.3 Aromatization

9.1.3.1 Method 1: Isomerization of Oxiranylidenes

9.1.3.2 Method 2: β-Elimination Reactions of Oxiranes

9.1.3.3 Method 3: Cycloreversion Reactions of Fused Oxiranes

9.2 Product Class 2: Thiirenes and Their Derivatives

N. Tokitoh and W. Ando

9.2 Product Class 2: Thiirenes and Their Derivatives

9.2.1 Product Subclass 1: Thiirenes

9.2.1.1 Synthesis by Ring Transformation

9.2.1.1.1 Method 1: From 1,2,3-Thiadiazoles

9.2.1.1.1.1 Variation 1: Photochemical Decomposition in Matrixes

9.2.1.1.1.2 Variation 2: Photochemical Decomposition in Solution

9.2.2 Product Subclass 2: Thiirene 1,1-Dioxides

9.2.2.1 Synthesis by Ring-Closure Reactions

9.2.2.1.1 Method 1: From α,α′-Dihalo-Substituted Sulfones

9.2.2.2 Aromatization

9.2.2.2.1 Method 1: Dehydrohalogenation of 2-Halothiiranes

9.2.3 Product Subclass 3: Thiirene 1-Oxides

9.2.3.1 Synthesis by Ring-Closure Reactions

9.2.3.1.1 Method 1: From α,α′-Dihalo-Substituted Sulfoxides

9.2.3.2 Aromatization

9.2.3.2.1 Method 1: Fused Thiirene 1-Oxides from Diels–Alder Reactions of 2,3-Bis(alkylidene)thiirane 1-Oxides

9.2.4 Product Subclass 4: Thiirenium Ions

9.2.4.1 Synthesis by Ring-Closure Reactions

9.2.4.1.1 Method 1: Addition of a Sulfonium Ion to Alkynes

9.2.4.1.2 Method 2: From 1-Halo-2-sulfanylethenes

9.3 Product Class 3: Selenirenes

N. Tokitoh and W. Ando

9.3 Product Class 3: Selenirenes

9.3.1 Synthesis by Ring Transformation

9.3.1.1 Method 1: From 1,2,3-Selenadiazoles

9.3.1.1.1 Variation 1: Photochemical Decomposition in a Matrix

9.3.1.1.2 Variation 2: Photochemical Decomposition in Solution

9.4 Product Class 4: Tellurirenes

N. Tokitoh and W. Ando

9.4 Product Class 4: Tellurirenes

9.5 Product Class 5: 1 H-Azirines

K.-P. Zeller

9.5 Product Class 5: 1 H-Azirines

9.5.1 Synthesis by Ring-Closure Reactions

9.5.1.1 By Formation of Two N—C Bonds

9.5.1.1.1 Fragments C—C and N

9.5.1.1.1.1 Method 1: Reactions of Alkynes with Nitrenes or Nitrene Equivalents

9.5.1.1.1.1.1 Variation 1: Generation of Nitrene (NH) from Hydrazoic Acid

9.5.1.1.1.1.2 Variation 2: Generation of Nitrenes from Organic Azides

9.5.1.1.1.1.3 Variation 3: Oxidation of N-Aminophthalimides in the Presence of Alkynes

9.5.1.2 By Formation of One N—C Bond

9.5.1.2.1 Fragment N—C—C

9.5.1.2.1.1 Method 1: Cyclization of α-Imino Carbenes

9.5.1.2.1.1.1 Variation 1: Generation of α-Imino Carbenes from 1H-1,2,3-Triazoles

9.5.1.2.1.1.2 Variation 2: Generation of α-Imino Carbenes from α-Diazo Imines

9.5.1.2.1.1.3 Variation 3: Generation of Cyclic α-Imino Carbenes from 1 H-1,2,3-Benzotriazoles (Formation of 1H-Benzo[b]azirines)

9.5.1.2.1.1.4 Variation 4: Generation of Cyclic α-Imino Carbenes from Isatin and Its Derivatives (Formation of 1H-Benzo[b]azirines)

9.5.1.2.1.2 Method 2: Cyclization of Vinylnitrenes

9.5.1.3 By Formation of One C—C Bond

9.5.1.3.1 Fragment C—N—C

9.5.2 Synthesis by Ring Transformation

9.5.2.1 Method 1: Extrusion Reactions of Larger Heterocycles

9.5.3 Aromatization

9.5.3.1 Method 1: Isomerization of Cyclic Isomers

9.5.3.2 Method 2: β-Elimination from Aziridines

9.5.3.3 Method 3: Cycloreversion Reactions of Fused Aziridines

9.6 Product Class 6: Phosphirenes

H. Heydt

9.6 Product Class 6: Phosphirenes

9.6.1 Product Subclass 1: λ⁵-1H-Phosphirenes

9.6.1.1 Synthesis by Substituent Modification

9.6.1.1.1 Method 1: Reaction of λ³-1H-Phosphirenes with Benzo-1,2-quinones

9.6.1.1.2 Method 2: Reaction of λ³-1H-Phosphirenes with Azodicarboxylates

9.6.1.1.3 Method 3: Modification of an Existing λ⁵-1H-Phosphirene

9.6.2 Product Subclass 2: λ⁵-1H-Phosphirene Imides, Oxides, and Homologues

9.6.2.1 Synthesis by Ring-Closure Reactions

9.6.2.1.1 By Formation of Two P—C Bonds

9.6.2.1.1.1 Method 1: Cycloaddition of Iminophosphines to Alkynes

9.6.2.2 Synthesis by Substituent Modification

9.6.2.2.1 Method 1: Oxidative Addition to λ³-1H-Phosphirenes

9.6.3 Product Subclass 3: λ⁵-1H-Phosphirenium Salts

9.6.3.1 Synthesis by Ring-Closure Reactions

9.6.3.1.1 By Formation of Two P—C Bonds

9.6.3.1.1.1 Method 1: Cycloaddition of Electrophilic Phosphorus Compounds to Alkynes

9.6.3.1.1.1.1 Variation 1: Cycloaddition with Phosphenium Cations

9.6.3.1.1.1.2 Variation 2: Cycloaddition with Halophosphines

9.6.3.1.1.1.3 Variation 3: Reaction with Dichlorophosphines

9.6.3.1.1.1.4 Variation 4: Reaction with Phosphiranium Cations

9.6.3.2 Synthesis by Substituent Modification

9.6.3.2.1 Method 1: Alkylation of λ³-1H-Phosphirenes

9.6.3.2.1.1 Variation 1: Alkylation with Alkyl Triflates

9.6.3.2.1.2 Variation 2: Alkylation with Trimethyloxonium Tetrafluoroborate

9.6.3.2.2 Method 2: Protonation of λ⁵-1H-Phosphirene Imides

9.6.4 Product Subclass 4: η-1H-Phosphirene-Metal Complexes

9.6.4.1 Synthesis by Ring-Closure Reactions

9.6.4.1.1 By Formation of Two P—C Bonds

9.6.4.1.1.1 Method 1: Cycloaddition of Phosphinidene Complexes to Alkynes

9.6.4.1.1.1.1 Variation 1: With Phosphinidene Complexes Generated from 7-Phosphabicyclo[2.2.1]hepta-2,5-diene Complexes

9.6.4.1.1.1.2 Variation 2: With Phosphinidene Complexes Generated from λ³-1H-Phosphirane Complexes

9.6.4.1.1.1.3 Variation 3: With Phosphinidene Complexes Generated from λ³-2H-1,2-Azaphosphirene Complexes

9.6.4.1.1.1.4 Variation 4: With Phosphinidene Complexes Generated from Secondary λ³-Phosphine Complexes

9.6.4.1.1.1.5 Variation 5: With Phosphinidene Complexes Generated from Disodium Tetracarbonylferrate (Collman's Reagent) and an Aminodichlorophosphine

9.6.4.2 Synthesis by Substituent Modification

9.6.4.2.1 Method 1: Exchange Reactions with the Substituent at Phosphorus

9.6.4.2.2 Method 2: Modification of the Metal Fragment

9.6.4.2.3 Method 3: Formation of ηH-Phosphirene-Metal Complexes by Complexation of λ³-1H-Phosphirenes

9.6.5 Product Subclass 5: λ³-1H-Phosphirenes

9.6.5.1 Synthesis by Ring-Closure Reactions

9.6.5.1.1 By Formation of Two P—C Bonds

9.6.5.1.1.1 Method 1: Cycloaddition of Phosphinidenes to Alkynes

9.6.5.1.1.2 Method 2: λ³-1H-Phosphirenes from Metallacyclopropenes

9.6.5.1.1.3 Method 3: λ³-1H-Phosphirenes from a Vinylcarbene-Cobalt Complex

9.6.5.1.2 By Formation of One P—C and One C—C Bond

9.6.5.1.2.1 Method 1: Cycloaddition of Carbenes to Phosphaalkynes

9.6.5.1.2.1.1 Variation 1: Cycloaddition with Halocarbenes

9.6.5.1.2.1.2 Variation 2: Cycloaddition with Chloro(vinyl)carbenes

9.6.5.1.2.1.3 Variation 3: Cycloaddition with a Stable Phosphino(silyl)carbene

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