With sulfur ylides

Ring expansion of activated aziridines (43) with sulfur ylides also provides a synthesis of azetidines (75JOC2990, 58BSF345, 81CC417). The highly reactive sulfonium methylide (44 R = R = H) undergoes further reaction with the azetidines (46), but the reaction is satisfactory for substituted methylides. The less reactive sulfoxonium methylide (45 R = R = H)... 

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. 

Cyclic dinuclear ylide complexes have also been prepared with sulfur ylides. The reactions of (dppm)(AuCl)2 or (dppe)(AuCl)2 with trimethylsulfoxonium tetrafluoroborate and base under phase-transfer conditions gave the products shown in Scheme 42. Auration of the dppm ligand leads to the byproducts.27... 

Closely related with the synthesis of ylides from carbenes is the use of ylides as carbene transfer reagents (CTR), that is processes in which the ylide is cleaved homolytically, liberating the nucleophile and the carbene, which could remain both coordinated to the metal or not (Scheme 10). Diphosphirane (34) can be obtained from the diphosphene by reaction with sulfur ylide Me2S(0)=CH2, which behave as a carrier of the CH2 unit [95]. Recent work of Milstein et al. shows that sulfur ylides decompose in the presence of Rh derivatives with vacant coordination sites affording Rh(l)-carbene complexes [96, 97]. Complexes (35-37) can be obtained from... 

The reduction of trifluoromethylimines with Mg(0) affords A-silyl difluoroena-mines." These synthons are very interesting for the preparation of difluoro- S-amino alcohols and of difluoro amino acids (cf. Chapter 4). They can also add onto radicals, react with sulfur ylides to afford difluoromethylaziridines, or even undergo intramolecular ene reactions (Figure 2.26)." ... 

Double-bond compounds that undergo the Michael reaction (5-17) can be converted to cyclopropane derivatives with sulfur ylides.1068 Among the most common of these is di-methyloxosulfonium methylide (108),l,l6, which is widely used to transfer CH2 to activated... 

Diazoalkanes, treated with sulfur, give episulfides.772 It is likely that R2C=S is an intermediate, which is attacked by another molecule of diazoalkane, in a process similar to that shown in 6-61. Thioketones do react with diazoalkanes to give episulfides.773 Thioketones have also been converted to episulfides with sulfur ylides.758... 

Kinetic control and thermodynamic control account, respectively, for epoxide formation and cyclopropanation [204]. Various Michael acceptors have been converted to cyclopropane derivatives with sulfur ylides. Some of the reagents used to transfer CHCOR [456], CHCOOR [457], CHMe... 

Reactions with sulfur ylides proceed differently. The products are oxacyclo-propanes (oxiranes) —not alkenes. The addition step proceeds as with the phosphorus ylides, but the negatively charged oxygen of the dipolar adduct then displaces the sulfonium group as a neutral sulfide. This is an intramolecular Sn2 reaction similar to the formation of oxacyclopropanes from vicinal chloroalcohols (Section 15-11C) ... 

The reaction of optically active (l-diethoxyphosphoryl)vinyl p-tolyl sulfoxide (20) with sulfur ylides has provided the corresponding cyclopropanes (21) in high yields (g) (Scheme 10).52,53 With fully deuterated dimethyl(oxo)sulfonium methylide, (CD3)2 S(0)CD2, the cyclopropanation reaction occurred in a highly diastereoselective... 

The first reaction of aminals with sulfur ylides to afford aziridines has been reported <070L2099>. The Ellman /er/-butylsulfinyl auxiliary group provided up to greater than 95 5 dr for trans and always greater than 95 5 dr for cis when allyl-, aryl-, and amide-stabilized ylides were employed. 

The reactions of thiopyrylium ions with sulfur ylides have been also investigated. Thus 2,4,6-triphenylthiopyrylium cation (9) reacts with Me2S (0)CH2 or with MeS (R)CH"COPh (R = Me, Ph) to yield compound 358 with X = H or COPh, respectively [72C1(L)498 80NKK604]. The reaction with the latter reagents also occurs with 2,3,4,6-tetraphenyl-thiopyrylium cation (313) (80NKK604). 

The reactions of allenic as well as of acetylenic Michael acceptors with sulfur ylides usually afford vinylogously stabilized ylides in place of the expected three-membered ring products This is due to the rapid proton shift in the zwitterionic intermediates. The in situ generation of the requisite Michael acceptor may be accomplished by utilizing masked enones, namely, the Mannich bases (equation 78). Since the oxosulfonium salts undergo... 

Compounds with the oxirane rings are special cases which, beside this general methodology, are also prepared by a number of other methods (direct epoxidation, reaction with sulfur ylides, Darzens reaction, etc.) [1]. 

Dithioesters like (62) which can exist in the enol form react with sulfur ylides like dimethylsulfoxonium methylide (63) to give ketenethiols (64). The mechanism of the reaction involves nucleophilic attack by the ylide on the enol form of (62) (Scheme 34). Similar compounds (65) may be synthesised by treatment of a suitable thioester (62) with an alkyl halide in the presence of a base (Scheme 35). 

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