Sulfur cyclopropanations with

Fig. 18. Product distribution from the reaction of cyclopropane with hydrogen as a function of sulfur coverage over a Ni(l 11) catalyst. Temperature = 550K. Total pressure = 100 torn Hj/cyclopropane = 100. From Ref. 4.)...

Ring closure is a common feature of the reaction of sulfur tetrafluoride with cyclopropane-, cyclobutane- and cyclopentanepolycarboxylic acids. This tendency seems to be enhanced by steric crowding. Thus, m,tricarboxylic acid gives a 1 1 mixture of cyclic ether 13 and cis,trims-], 2,3-tris(trifluoromethyl)cyclopropane, whereas cyclopropane-... 

Ring expansion reactions are much better known and sulfolene substrates have received considerable investigation. Cyclopropanation with dichlorocarbene affords 6,6-dichloro-3-thiabicyclo[3.1.0]hexane 3,3-dioxides which may readily be ring enlarged by base or acid treatment. Base treatment, especially with LDA, cleanly affords 2//-thiopyran dioxides hydrochloric acid does likewise, but less cleanly, while hydrobromic acid treatment causes a more complex set of reactions leading to thiopyranones containing bromine in which the sulfur has been reduced. The intermediacy of thiopyrylium oxides has been invoked to rationalize the observations (Scheme 27) (81JOC4502). 

The reaction of sulfur ylides with enones gives cyclopropanes. 

Cyclopropanes with sulfur substituents have received much interest in synthetic chemistry. Two recent studies of sulfmyl and sulfonyl derivatives will be mentioned here. Relative configurations of two diastereomers of 118 have been determined by The... 

The opening of activated cyclopropanes with nitrogen nucleophiles has been widely applied to the synthesis of pynolizidine and pyrroline alkaloids by Danishefsky this subject has been reviewed. A number of pyrroline annulations have been based on this principle, illustrated in equation (35a). > Similar opening can be accomplished with halides, cuprates, and sulfur or selenium nucleophiles. ... 

Reaction of cyclopropane with aqueous sulfuric acid results in a small amount of exchange into unreacted cyclopropane and for the reaction is 1.56. These... 

The electron-deficient double bond in 2-phenylsulfonyI-l,3-dienes underwent regioselective cyclopropanation with sulfur ylides in very good yield, e.g. cyclopropanation of 13, 14 and 15 with sulfur ylides.On the other hand, the use of zinc-copper couple and diiodomethane afforded a 83 17 mixture of vinylcyclopropanes 16 and 17 from 2-(phenylsulfonyl)cyclohexa-1,3-diene (15) in moderate yield. The reaction at the electron-deficient double bond rather than at the expected electron-rich double bond shows that the Simmons-Smith carbenoid is fairly nucleophilic in character. 

Under similar conditions, no cyclopropanation of allyl phenyl sulfones takes place, but rather [2,3] rearrangement of a primarily formed sulfur ylide. With but-2-enenitrile, oxazole formation rather than cyclopropanation occurs. " ... 

Anionic rearrangement of sulfonium ylides and anions of sulfides are well exemplified. It has been reported that base-catalyzed ring contraction of 3-alkyl- and 2,3-dialkyIthietane 1-oxides, prepared by peroxyacid oxidation of the corresponding substituted thietanes, gave substituted cyclopropanes with stereoselectivity controlled by the configuration of the sulfur... 

When trifluoroacetic acid was added to butylcyclopropane derivatives 12, Markovnikov products were obtained predominantly. Treatment of cyclopropane with concentrated sulfuric acid yielded propanol. With the deuterated acid, D2SO4, deuterium was found at all three carbon atoms presumably due to the formation of a protonated cyclopropane intermediate. When exo-tricyclo[3.2.1.0 ]octane (13) was treated with deuterated sulfuric acid an end-on attack of the deuterium ion at the most strained bond with inversion of configuration to give 14 was observed. 

Sulfur ylides are useful as nucleophilic alkylidene transfer agents in reactions with electron-deficient functional groups, forming epoxides with carbonyls, and either undergoing carbonyl addition with epoxide formation or conjugate addition with cyclopropanation with Michael acceptors, depending on the structure of the Michael acceptor [113]. 

An alternate approach, pioneered by Kunz and MacMillan, proceeds by reaction of sulfur ylides with a,(3-unsaturated iminium ions, formed by reaction of a,p-enals with enantiomerically pure amines. In this approach the sulfur ylide (9.87) reacts with a range of (3-aryl- and P-alkyl-substituted enals, including (9.88), in the presence of the dihydroindole (9.89) to give the cyclopropane with ees ranging from 89 to 96%. More recently, it has been shown that replacement of the carboxylate functional group in (9.89) with an isosteric tetrazolic acid gives an improved catalyst that effects cyclopropanation with 99% ees in all cases studied. 

The one-pot synthesis of dibenzoyl cyclopropanes with a cis trans stereoselectivity by Wittig olefination-sulfur ylide cyclopropanation sequence has been described. When 0 CS2CO3 was used as the base and CHjCN/water (8 2, v/v) as the solvent, the major product was the c -1,2-dibenzoyl cyclopropane. In contrast, when using DBU as the base and MeOH as the solvent, the major product was fra i-dibenzoyl cyclopropane. 

The reaction of sulfur dioxide with cyclopropanes in trifluoroacetic acid at 20 °C affords mixtures of isomeric 1,2-oxathiolane 2-oxides (y-sultines). From cis-1,2-diphenylcyclopropane a mixture of the (2,3-cw)-2-oxide 19 (yield, 52 %) and the (2,3-trans)-2-oxide 20 (yield, 18 %) is obtained... 

The Corey-Chaykovsky reaction entails the reaction of a sulfur ylide, either dimethylsulfoxonium methylide (1, Corey s ylide, sometimes known as DMSY) or dimethylsulfonium methylide (2), with electrophile 3 such as carbonyl, olefin, imine, or thiocarbonyl, to offer 4 as the corresponding epoxide, cyclopropane, aziridine, or thiirane. ... 

Abstract The photoinduced reactions of metal carbene complexes, particularly Group 6 Fischer carbenes, are comprehensively presented in this chapter with a complete listing of published examples. A majority of these processes involve CO insertion to produce species that have ketene-like reactivity. Cyclo addition reactions presented include reaction with imines to form /1-lactams, with alkenes to form cyclobutanones, with aldehydes to form /1-lactones, and with azoarenes to form diazetidinones. Photoinduced benzannulation processes are included. Reactions involving nucleophilic attack to form esters, amino acids, peptides, allenes, acylated arenes, and aza-Cope rearrangement products are detailed. A number of photoinduced reactions of carbenes do not involve CO insertion. These include reactions with sulfur ylides and sulfilimines, cyclopropanation, 1,3-dipolar cycloadditions, and acyl migrations. 

Double-bond compounds that undergo the Michael reaction (15-21) can be converted to cyclopropane derivatives with sulfur ylids. Among the most common of these is dimethyloxosulfonium methylid (109), which is widely used to... 

The above relationships between the thiiranes (20) and their dioxides (17) are reminiscent of those between cyclopropane and cyclopropanone. The entire phenomena of the C—C bond lengthening and the concomitant C—S bond shortening in the three-membered ring sulfones and sulfoxides can be accounted for in terms of the sulfur 3d-orbital participation and the variation in the donor-acceptor capacities of the S, SO and S02 . The variations of the calculated valence-state orbital energies, together with the corresponding variations of the C—C overlap populations, can be used to understand the discontinuous variations of the C—C and the C—S bond lengths in the series thiiranes -... 

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