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Page 2 of 20 Wang et al. Chem Synth 2023;3:12 https://dx.doi.org/10.20517/cs.2023.01

INTRODUCTION
Sulfur-containing compounds are very important in organic chemistry, not only because of their prevalence
[1-3]
in a number of fascinating natural products, clinical drugs, and pharmaceutical candidates , but also due
to their applicability as chiral auxiliary, chiral ligands, or chiral organocatalysts for various asymmetric
[4-6]
transformations . Actually, a large number of organosulfur reagents have been identified and confirmed
[7,8]
as versatile reactants for many different kinds of reactions . However, among the diverse prominent
organosulfur reagents, sulfur-based ylides should belong to the most important and widely-used sulfur-
containing reactants in the realm of organic synthetic chemistry. Through literature survey and search, it
was found that since the pioneering work of Ingold and Jessop and the groundbreaking work of Johnson
[9]
[10]
and Lacount , Corey and Chaykovsky in the 1960s [11-14] , the study on sulfur-based ylides chemistry has
achieved an impressive development during the past nearly 60 years [15-19] . In this area, especially, stabilized
sulfonium and sulfoxonium ylides bearing a carbonyl group at the α-carbon atom [Figure 1] have occupied
a dominant position, probably due to some of their inherent characteristics including thermal stability, easy
preparation and use, and low toxicity, as well as owing to their powerful functions as nucleophilic 1,1’-
dipolar species for realizing numerous chemical transformations. Moreover, with the rapid development of
catalytic asymmetric synthesis, several stereocontrolled strategies, including asymmetric organometallic
catalysis and organocatalysis, have been implemented in the reactions involving sulfonium and sulfoxonium
ylides for the construction of chiral compounds.

With the increase of reports on various reactions involving sulfonium and sulfoxonium ylides, several
reviews concerning the application of sulfonium and sulfoxonium ylides in organic synthetic chemistry
have been published in recent years. In 2017, Lu et al. summarized the catalytic cyclization reactions of
[20]
sulfur ylides . In 2018, Neuhaus et al. reported the developments in the transition metal-catalyzed
reactions involving sulfonium and sulfoxonium ylides . One year later, a review on the bond-forming and
[21]
-breaking reactions from organic sulfur(IV) molecules including sulfonium salts and sulfur ylides was also
published from the same group . Subsequently, the versatile applications of sulfoxonium ylides in organic
[22]
synthesis were also reviewed by Bernardi’s and Burtoloso’s groups, respectively [23,24] . In addition, Fan et al.
also published an overview of sulfonium salt and sulfur ylide chemistry . Although these reviews have
[25]
been published, a critical survey of the literature reveals that there are a lot of elegant works on the catalytic
asymmetric reactions of sulfonium and sulfoxonium ylides by organocatalysis has been reported, but no
special review summarizes these works. In this context, based on a serious consideration involving the rapid
development of asymmetric organocatalysis and the wide application of sulfur-based ylides in organic
synthesis, a comprehensive review on this aspect is needed.

It is an indisputable fact that asymmetric organocatalysis has emerged as a powerful strategy in organic
synthesis for the construction of chiral molecule scaffolds since the early 2000s [26-29] . In this research area, a
large number of outstanding achievements have been made from various aspects. Many useful reagents
have been successfully applied to diverse organocatalyzed asymmetric reactions, and the sulfonium and
sulfoxonium ylides are not an exception. In this review, we will comprehensively present the application of
sulfonium ylides and sulfoxonium ylides in asymmetric chemical transformations with organocatalysis
tactics. In addition, the substrate scope, possible mechanism, transition states, and synthetic applications are
also introduced. For better understanding, this review is classified into two main sections according to the
type of sulfur-based ylides: (1) organocatalytic asymmetric reactions of sulfonium ylides; (2) organocatalytic
asymmetric reactions of sulfoxonium ylides. In each section, the reaction types include both asymmetric X-
H (X = C, N, S) bond insertion reactions and asymmetric cyclization reactions [Figure 2]. In addition, it
should be declared here that this review only focuses on the organocatalytic asymmetric reactions where
involving preformed sulfonium ylides and sulfoxonium ylides as reactants, but the reactions where the sulfur