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

Figure 1. Representative structures of sulfonium and sulfoxonium ylides.

Figure 2. Application of sulfonium and sulfoxonium ylides in the asymmetric reactions by organocatalysis.

ylides participated in the transformations are generated in-situ from the corresponding salt precursors
under basic conditions are not discussed [30-33] . Nevertheless, the related asymmetric reactions with chiral
sulfide-centric catalysts involving chiral sulfur ylide intermediates [34-39] and those with chiral auxiliary-
derived sulfonium salts as reactants are also not discussed here. This arrangement is mainly based on the
consideration that those reactions were well described in previous elegant reviews [15,16,40,41] .

ORGANOCATALYTIC ASYMMETRIC REACTION OF SULFONIUM YLIDES
Sulfonium ylides can be represented by ylide form which contains a carbanion connecting a positively
charged sulfur (IV) atom, or by ylene form which contains a C = S(IV) double bond [Figure 1]. The stability
of sulfonium ylides depends largely on the degree of electron delocalization on the carbanion center.
Therefore, stabilized sulfonium ylides generally bear an electron-withdrawing functional group connected
to the carbanion center; thus, these ylides are readily prepared and usually used in various reactions. The
stabilized -carbonyl sulfonium ylides can be applied as one-carbon synthons to construct C-X (X = C, N, S)
bonds [17,40,42] . Moreover, they are more commonly used in cyclization reactions with electron-poor π-systems
for the synthesis of various ring compounds [20,22] . In the area of organocatalysis, stabilized sulfonium ylides
have been used in N-H bond insertion reactions, cyclopropanation reactions, and [4 + 1] cyclization
reactions under the promotion from various organocatalyst via different activation patterns.

Asymmetric N-H bond insertion reaction
Chiral organocatalysts promoted asymmetric heteroatom-H bond insertion reaction with the sulfonium
ylides remained highly challenging in the past two decades, and successful research was virtually
nonexistent. Until 2020, Guo et al. disclosed the asymmetric N-H bond insertion reactions by -carbonyl
sulfonium ylides using chiral phosphoric acids as catalysts, affording a series of chiral -amino ketone
compounds with excellent efficiency and enantioselectivity [Figure 3] . Under conditions A or B, the
[43]
transformation with -methyl sulfonium ylides 1 as substrates proceeded smoothly to form α-tertiary amino
ketones 3 in 40%-79% yields with 78%-99% ee. As for the α-non-methyl sulfonium ylide or cyclic sulfonium
ylide substrates, the reaction with condition B could give the corresponding α-amino ketones 4 bearing
various alkyl chains or Cyclic α-amino ketones in 49%-94% yields with 80%-98% ee. In addition, α-alkyl
esters derived sulfonium ylides 1 could also act as available starting materials to participate in the N-H bond