Sulfur-Based Ylides in Transition-Metal-Catalysed Processes

Abstract

Traditionally employed in the synthesis of small ring systems and rearrangement chemistry, sulfur-based ylides occupy a unique position in the toolbox of the synthetic organic chemist. In recent years a number of pioneering researchers have looked to expand the application of these unorthodox reagents through the use of transition metal catalysis. The strength and flexibility of such a combination have been shown to be of key importance in developing powerful novel methodologies. This chapter summarises recent developments in transition metal-catalysed sulfonium/sulfoxonium ylide reactions, as well as providing a historical perspective. In overviewing the successes in this area, the authors hope to encourage others into this growing field.

Keywords: Asymmetric catalysis; Historical perspective; One-carbon synthon; Recent developments; Sulfonium ylides; Sulfoxonium ylides; Transition metal catalysis.

Scheme 1

Sulfonium ylides complexes as cross-coupling catalysts. DMF Dimethylformamide

Scheme 2

The first Cu-promoted formal (4 + 1) cycloaddition

Fig. 1

Chiral Lewis acid-promoted, formal (4 + 1) cycloaddition

Scheme 3

Scope of dihydropyrazole formation

Scheme 4

Palladium-catalysed decarboxylative (4 + 1) for the asymmetric synthesis of indolines

Fig. 2

The mechanism of Pd-catalysed decarboxylative formal (4 + 1) cycloaddition

Scheme 5

Iron-catalysed decarboxylative formal (4 + 1) cycloadditions. TBAFe Bu₄N[Fe(CO)₃(NO)]

Scheme 6

Copper-catalysed decarboxylative formal (4 + 1) cycloadditions. THF Tetrahydrofuran

Fig. 3

Copper-allenylidene intermediates in decarboxylative formal (4 + 1) cycloadditions

Scheme 7

Doyle’s Cu-catalysed asymmetric formal (3 + 1) cycloaddition. RT Room temperature

Fig. 4

Mechanism of the formal (3 + 1) cycloaddition involving sulfonium ylides

Scheme 8

Skrydstrup’s intermolecular furan synthesis. DCE 1,2-Dichloroethane

Scheme 9

Maulide’s intramolecular furan synthesis

Fig. 5

Proposed mechanisms for furan formation

Scheme 10

Intermolecular synthesis of trisubstituted furans

Scheme 11

Maulide’s intermolecular furanone formation

Scheme 12

Maulide’s Au-promoted intramolecular cyclopropanation

Scheme 13

Domino deracemisation/cyclopropanation of sulfonium ylides

Fig. 6

Mechanistic rationale behind the deracemisation/cyclopropanation cascade

Scheme 14

Intermolecular cyclopropanation of allenamides

Scheme 15

Gold-catalysed [1,4] vinyl migration

Scheme 16

Sulfoxonium ylides as precursors for the Rh-catalysed formation of napthols

Fig. 7

Proposed mechanism of naphthol formation. DMSO Dimethyl sulfoxide

Scheme 17

Simultaneously disclosed Rh-catalysed formal C–H insertion reactions. HFIP Hexafluoroisopropanol

Fig. 8

Mechanism of formal C–H insertion of sulfoxonium ylides

Scheme 18

Pd-catalysed sulfur-to-silicon group transfer. GC-MS Gas chromatography–mass spectrometry

Scheme 19

C–S bond activation for the methylation of terminal alkynes

Scheme 20

Xiao’s photocatalytic insertion of sulfonium ylides into C–H bonds for oxindole synthesis [48]. LEDs Light-emitting diodes

Fig. 9

Mechanism of the photocatalysed C–H insertion. LEDs Light-emitting diodes

Scheme 21

Photocatalytic synthesis of 2,3-disubstituted indoles

Fig. 10

Mechanism of the photocatalysed synthesis of 2,3-disubstituted indoles

Scheme 22

Initial investigations towards the use of sulfonium ylides as diazo surrogates

Scheme 23

Asymmetric metal-catalysed cyclopropanations

Scheme 24

Iron-catalysed carbenoid transfer to generate CF₃-substituted cyclopropanes. DMA Dimethylacetamide

Scheme 25

Rhodium- and iridium-catalysed X–H bond insertion reactions

Scheme 26

Iridium-catalysed N–H insertion in the synthesis of biologically relevant targets. DMF Dimethylformamide

Scheme 27

Ligand effects in X–H insertion reactions

Scheme 28

Hopmann’s N–H insertion for indole synthesis. p-TSA p-Toluenesulfonic acid

Scheme 29

Limitations in C–H insertion reactions

Scheme 30

Iridium-catalysed C–H insertion for pyrrole synthesis

Scheme 31

Thermal versus photochemical formation of sulfonium ylides

Fig. 11

General mechanism for the metal-catalysed synthesis of sulfonium ylides from diazo compounds

Fig. 12

General proposed mechanism for the Doyle–Kirmse reaction

Scheme 32

Iron-catalysed Doyle–Kirmse reaction of allyl and propargylsulfides

Scheme 33

Highly chemoselective TBAFe-catalysed Doyle–Kirmse reaction

Scheme 34

Rhodium-catalysed thia Sommelet–Hauser rearrangement of benzylsulfides

Scheme 35

Wang’s modified Gassman oxindole synthesis

Scheme 36

Enantioselective Doyle–Kirmse reaction by Uemura and co-workers

Fig. 13

Plausible reaction pathways in enantioselective metal-catalysed Doyle–Kirmse reactions

Scheme 37

Cobalt salen-catalysed Doyle–Kirmse reaction

Scheme 38

Difference in enantio-induction starting from non-symmetric and symmetric allylsulfides

Fig. 14

Evidence of the strong affinity of sulfonium ylides for electrophilic copper complexes

Scheme 39

Double asymmetric induction in copper-catalysed Doyle–Kirmse reaction

Scheme 40

Enantioselective Doyle–Kirmse reaction under full catalyst control

Scheme 41

In situ generation of diazo compounds in the Doyle–Kirmse synthesis of thioether imines

Scheme 42

Doyle–Kirmse reactions from in situ-generated (2-furyl)carbenoids

Scheme 43

Alkynes as masked ylides in Doyle–Kirmse chemistry

Scheme 44

Synthesis of sulfur heterocycles from alkynyl sulfoxides

Scheme 45

Doyle–Kirmse reaction from cyclopropenes

Scheme 46

Macrocycle ring expansion by the double Stevens rearrangement

Scheme 47

Proposed synthesis of Nuphar thioalkaloids through ring expansion of thietanes

Scheme 48

Stevens rearrangement as a key step in the formal synthesis of (+)-Laurencin

Scheme 49

Copper-catalysed enantioselective 1,2-migration of dithioacetals

Scheme 50

Chemoselectivity between 1,2-migration and Sommelet–Hauser rearrangement

Scheme 51

Diazo-based and diazo-free sulfide-mediated epoxidation of aldehydes

Fig. 15

Camphor-derived chiral sulfides for epoxidation, aziridination and cyclopropanation

Scheme 52

Rhodium-catalysed formation of thiocarbonyl ylides for electrocyclisation and cycloaddition reactions