Sulfides carbene transfer

Ylide Reaction. Yllde formation in catalytic carbene transfer reactions has attracted considerable attention in the past decade. The ylide can be easily generated from a metal carbene and a Lewis base, such as carbonyl compound or sulfide. The highly reactive ylide then proceeds to undergo further reactions. For example, diazoacetic ester (10) is prepared from -phenylthio-2,3-O-isopropylidene D ribofuranose and compound (1). Decomposition of (10) in refluxing benzene containing rhodium(II) acetate results in lactone (11) via an eight-membered cyclic sulfoniumyUde intermediate (eq 9). ... 

Rhodium(II) carbenoid intermediates are also useful. For example, carbene transfer reaction with allylic sulfides followed by [2,3]-sigmatropic rearrangement of the resulting sulfur ylides (Doyle-Kirmse reaction) gives furan-containing sulfides 133 in good yields (Scheme 19.32) [50]. In contrast, reaction with allylic compounds (R—H) or alcohols/amines/thiols/silanes (X—H) furnishes the 1,1-insertion products 134 or 135, respectively [51],... 

Catalysis via Transition Metal-Mediated Carbene Transfer to Sulfides... 

In catalytic epoxidation reactions an alternative to the ylide generation method via alkylation/deprotonation is the transition metal-mediated carbene transfer from diazo compounds to sulfide catalysts. In 1994, Aggarwal and coworkers employed this method in the enantioselective catalytic epoxidation of aldehydes [25]. Using 20mol% of non-racemic sulfide 17 and lmol% of Rh2(OAc)4 together with the slow addition of PhCHN2, a 58% yield and 11% ee were obtained in the epoxidation of benzaldehyde (Scheme 20.10). The enantioselectivity was similar to the results obtained by Breau and Durst using preformed sulfonium salts [26]. 

The sulfide-catalyzed enantioselective epoxidation reaction is the most extensively studied transformation in ylide catalysis, and two ylide generation methods (aUcylation/deprotonation and carbene transfer) have been developed. Compared with conventional methods for epoxidation via oxygen transfer to the carbon-carbon double bond, such as the Sharpless epoxidation, Jacobsen-Katsuki epoxidation, and Shi epoxidation, the yhde approach can be regarded as an alkyUdene transfer reaction to carbonyl groups (C=0), providing a different retrosynthetic analysis for the construction of epoxides. In particular, in the synthesis of vinyl epoxides, the ylide route has priority over conventional oxidation methods, since the issue of regjoselectivity in the epoxidation of dienes will not be present [32]. 

Ylide generation via carbene transfer also works weU for the aziridination of N-sulfonyl-imines [37]. With 20mol% sulfide 18b as the catalyst, the reactions of SES-protected imines with diazomethylbenzene provided the aziridine products... 

A solid-liquid phase-transfer technique is used to synthesize aryl difluoro-methyl sulfides and selenides thiophenols dissolved in an aromatic solvent are treated with solid sodium hydroxide in the presence of a catalytic amount of tris(3,6-dioxaheptyl)amine (TDA1) [49] This condensation proceeds by a carbene mechanism (equation 44)... 

The enol form of mandelic acid (101) has been generated by flash photolysis of phenyldiazoacetic acid in aqueous solution.101 The enol forms by hydration of the intermediate carbene (102). The reaction of chloramine-T (TsNClNa O) with methyl p-tolyl sulfide to give the corresponding sulfimide (103) appears to proceed via a nitrene-transfer mechanism in the presence of copper(I) and a second nitrogen ligand (such as acetonitrile).102... 

The addition of a carbene or benzyne to a sulfide, and to a lesser extent to an amine, provides a direct route to ylides. Enormous progress has been realized with this approach, mainly as a result of the efforts of Ando and Doyle. Most noteworthy amongst examples using benzyne is die squalene synthesis reported by Ollis, in which the sulfide (55) was transformed by a 3,2-rearrangement into the squalene precursor (58) and eventually into squalene itself (Scheme The stereospecific rearrangement of cjco-methylenecyclohexane derivatives discovered by Evans employed dichlorocarbene, generated under phase transfer conditions (Scheme 15). ... 

---