Preface

Dioxiranes are multitasking agents capable of several types of transformation, both in stoichiometric and catalytic amounts. The dioxiranes are prepared from the reaction of a ketone with caroate (a salt of Caro’s acid). While the residue of caroate is considered eco-friendly, acetone and natural carbohydrate-derived-ketones are also environmentally benign. The contemporary use/development of synthetic methodologies is focused on inexpensive, user-friendly and eco-friendly protocols. The United Nations (UN) Sustainable Development Goals (SDGs) are focused on making our environment pollution-free and healthy for all living beings. Organic synthesis has become an important tool to access a myriad of compounds for the material world in application to medicines, food, cosmetics, fertilizers, organic light-emitting diodes, organic solar cells, etc.

In this book, our effort is to consolidate and deliver a comprehensive overview of the chemistry of dioxiranes. The research on dioxirane over more than five decades has been collated with more than 400 references. The discovery, characterization, and isolation of dioxiranes are illustrated. The mechanistic aspects are included wherever necessary. The peroxy-linkage present in dioxiranes makes them an excellent oxygen donor, i.e., oxygenation agent. Although these were proposed earlier by Baeyer and Villiger, the first-time synthesis was achieved in 1972. Afterward, different types of efficient dioxiranes have been prepared with higher reactivity and selectivities to tune this peroxy-linkage. In addition, heteroatom dioxirane, where the C-atom of the dioxirane ring is replaced with a heteroatom like N, P, S, Si, etc.

The application of dioxirane is very vast, for example, the dioxirane-mediated oxidations have been performed for a variety of functional groups such as amines, anilines, isocyanate, sulfides, thiols, disulfides, thioketones, sulfilimines, selenoesters, alcohols, phenols, boronic acids, boronates, iodo-compounds, phosphines and silane compounds, etc.; the products have a myriad of applications. Similarly, epoxidations of various olefins, like alkenes and alkynes, are achieved with dioxiranes. Notably, regioselective, stereoselective, chemoselective, etc., types of epoxidations of alkenes are performed with dioxiranes. The asymmetric Shi epoxidation using catalytic chiral dioxirane precatalysts is included in the book. The epoxidation protocols applicable for the synthesis of biologically-relevant and natural products, like metabolites of Aflatoxin B1, Majucinoids, tetrahydrocannabinol, and pectenotoxins, are discussed. Furthermore, C-H functionalizations of unactivated centers with dioxiranes are covered. C-H oxygenations of primary, secondary and tertiary C-H bonds are successfully performed with dioxiranes. It is noteworthy to mention that the oxygenation of carbohydrates, amino acids, steroids and lipids is achievable with dioxiranes. Supramolecular hosts like α-, β- and γ-cyclodextrins (CDs), were used for site-selective hydroxylation. When a latent ketone chain is present on the substrate, intramolecular hydroxylation, oxygenation-cum-cyclization, and oxygenation-cum-lactonization can give synthetically useful compounds. Biologically relevant compounds like carbohydrates, ent-trachylobane, Eldecalcitol, bryostatin, Taxol^®, thujone, (+)-menthol, eudesmane, Spirochensilide A, Valinomycin, dafachronic acid, etc., were accessed using dioxiranes and are included in the book. The chiral precatalysts are useful for reactions involving asymmetrizations, kinetic resolutions, asymmetric and desymmetrizations.

With this book, we aim to bridge the laboratory research and industrial needs. Therefore, a special emphasis is made on the sustainable chemistry aspect and the synthesis of natural products and drugs. The book will therefore be useful to both beginners and experts in the field of organic chemistry.

We believe this book will serve as an important and useful resource in promoting future applications and innovations in the field of dioxirane chemistry. We thankfully acknowledge all the contributions of those chemists cited for their research in the field.

We are thankful to Aslam C. Shaikh, Department of Chemistry, IIT Ropar, for his humble support during book writing. We used ChemDraw 21.0.0 to draw all reactions and several structures in this book, which was very helpful.

We acknowledge the facility and infrastructure of IISER Thiruvananthapuram and CSIR-NIIST, which were very useful for preparing the book.