Advances in Organic Synthesis: Volume 9

Atta-ur-Rahman

• Publisher: Bentham Science Publishers
• Year: 2018
• ISBN:
  9781681086958
• Topic: Physical Sciences
• Subtopic: Organic Chemistry

Advances in Organic Synthesis is a book series devoted to the latest advances in synthetic approaches towards challenging structures. The series presents comprehensive reviews written by eminent authorities on different synthetic approaches to selected ta

Synthesis of N,O,S-Heterocycles by One-Pot Reactions of Epoxides, Aziridines and Oxaziridines

Oleksandr Zhurakovskyi¹, Vitalii Palchykov^{2, *}

¹ School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, UK

² Department of Chemistry, Oles Honchar Dnipro National University, Dnipro, 49010, Ukraine

Abstract

Discovery of new effective methods for the synthesis of aziridines, epoxides and oxaziridines, as well as development of novel transformations of these heterocycles, has been an extremely active area of research in recent years. In just two or three steps, these small heterocycles can be converted into a vast array of four-to- seven-membered rings and open-chain compounds. The diversity of possible transformations transpired in a torrent of publications, with hundreds of papers published every year. This review covers recent (2007 to the end of 2017) literature on one-pot transformations of aziridines, epoxides, and oxaziridines. Within this, deceptively narrow, topic there is a great number of synthetically useful or mechanistically interesting reactions leading to diverse families of N,O,S-heterocycles, including thiiranes, oxetanes, azetidines, azetidinones, furans, 1,3-oxazolines, 1,3-oxazolidines, 1,3-oxazolidin-2-ones, 1,3-thiazolidines, imidazoles, 1,2,3-triazoles, pyrans, 1,4-oxazines (morpholines), azepanes, oxazepanes etc. The review aims to give the readers an insight into the great practical utility of epoxides, aziridines and oxaziridines. It presents the most modern methods for their expedited conversion into a broad range of heterocycles.

Keywords: Aziridines, Azetidines, Azetidinones, Azepanes, Cycloaddition, Epoxides, Furans, Imidazoles, Isomerization, N,O,S-heterocycles, Oxaziridines, Oxetanes, Oxazepanes, 1,3-Oxazolines, 1,3-Oxazolidines, 1,3-Oxazolidin-2-ones, 1,4-Oxazines (morpholines), Pyrans, Pyrrolidines, Pyrroles, Rearrangement, Ring expansion, Ring-opening reaction, Thiiranes, Transition-metal catalysis, 1,3-Thiazolidines, 1,2,3-Triazoles.

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^* Corresponding author Dr. Vitalii Palchykov: Department of Chemistry, Oles Honchar Dnipro National University, Dnipro, 49010, Ukraine; Tel: [phone]; E-mail: [email protected]

Introduction

Three-membered heterocycles offer a powerful combination of reactivity, stability, availability, and atom economy. As the result, their synthesis and

reactions have been regularly reviewed. A comprehensive review on three-membered rings was published by A. Yudin in 2006 [1], as a 500-page book which became a benchtop reference for many researchers. An update on the topic came out in 2014 in a special issue of Chemical Reviews, “Small heterocycles in synthesis” [2].

The aim of this chapter is not to provide an exhaustive list of all possible transformations. Instead, the report presents an overview of the most synthetically valuable and intriguing one-pot methods that pertain to the synthesis of 3-7 membered N,O,S-heterocycles and more large cycles. Also, this review will not discuss the well-known addition of carbon dioxide/carbon disulfide to epoxides and aziridines which gives cyclic carbonates and 1,3-oxazolidin-2-ones, respectively, since this topic has been discussed in great detail elsewhere [3^-11]. Further topical reviews will be mentioned in the text where appropriate.

Synthesis of 3-Membered Rings

One-pot interconversion of 3-membered heterocycles has been known since the early days of organic chemistry. However, with few exceptions, such reactions did not attract much interest, and alternative approaches have been used instead. One notable exception is the synthesis of thiiranes from epoxides, which became a method of choice for the preparation of these heterocycles.

Thiiranes

One-step preparation of thiiranes from epoxides (Scheme 1) has been known for a long time [12]. A detailed computational and experimental study was reported in 2009 by Schreiner, who managed to isolate a number of reaction intermediates [13]. He showed that the reaction proceeds “in water”, rather than “on water”, and depends greatly on the solubility of the starting epoxides.

Scheme 1)
Classical synthesis of thiiranes from epoxides.

This method became a staple for the synthesis of thiiranes. Multiple developments both of the sulfu...