Addition of Oxygen Nucleophiles

Other methods for the synthesis of a-oxygenated A-alkylamides (or carbamates) include addition of oxygen nucleophiles to A-acyl (or A-alkoxycarbonyl) iminium ions, generated via either... 

Hydration and Other Acid-Catalyzed Additions of Oxygen Nucleophiles... 

Phenylthio)nitroalkenes are also excellent intermediates for the synthesis of other heterocyclic ring systems. For example, tetrahydropyran carboxylic acid derivatives are formed by the intramolecular addition of oxygen nucleophile to l-(phenylthio)nitroalkene predominantly as the m-isomer (9.1 1) (see Eq. 4.40). The reaction may proceed via the chair-like transition state with two pseudo-equatorial substituents.50... 

Transition Metal-catalyzed Additions of Oxygen Nucleophiles to Alkynes 672... 

Addition of oxygen nucleophiles to alkynes via metal vinylidenes 676... 

Addition of Oxygen Nucleophiles to Transition Metal 7r-Arene Complexes 685... 

Baldwin, J. E. Thomas, R. C. Kruse, L. I. Silberman, L. Rules for ring-closure Ring formation by conjugate addition of oxygen nucleophiles. J. Org. Chem. 1977, 42, 3846-3852. 

SECTION 4.2. HYDRATION AND OTHER ACID-CATALYZED ADDITIONS OF OXYGEN NUCLEOPHILES... 

Palladium-catalyzed addition of oxygen nucleophiles to alkenes dates back to the Wacker process and acetoxylation of ethylene (Sects. 1 and 2). In contrast, catalytic methods for intermolecular oxidative amination of alkenes (i.e., aza-Wacker reactions) have been identified only recently. Both O2 and BQ have been used as oxidants in these reactions. 

It is interesting to note that the oxa-analogous Michael addition was reported for the first time in 1878 by Loydl et al. [19] in their work on the synthesis of artificial malic acid, which was five years ahead of the discovery of the actual Michael reaction described first by Komnenos [20], Claisen [21], and later Michael in 1887 [22] as one of the most important methods for C—C bond formation. In continuation of the early work on the oxa-Michael addition [23], the inter- and intramolecular additions of alkoxides to enantiopure Michael acceptors has been investigated, leading to the diastereo- and enantioselective synthesis of the corresponding Michael adducts [24]. The intramolecular reaction has often been used as a key step in natural product synthesis, for example as by Nicolaou et al. in the synthesis of Brevetoxin B in 1989 [25]. The addition of oxygen nucleophiles to nitro-alkenes was described by Barrett et al. [26], Kamimura et al. [27], and Brade and Vasella [28]. 

Finally, a,[3-unsaturated carbonyl compounds are converted to [3-keto systems when treated with 20% Na2PdCl4 catalyst in 50% acetic acid as solvent and r-butyl hydroperoxide or hydrogen peroxide as reoxidant (equation 3).9 It is not clear if the mechanism of this process is related to the other palladium(II)-catalyzed addition of oxygen nucleophiles to alkenes. 

The most intense interest in the addition of oxygen nucleophiles to Tr-allylpalladium complexes has centered on the delivery of OAc. For example, in allylpalladium-OAc complexes, acetate can be induced to migrate to the allyl ligand by the addition of CO (equation 46).162-164 Rearrangements and isomerizations of allyl acetates can also be readily accomplished via Pd catalysis (equations 47 and... 

The addition of oxygen nucleophiles (peroxides) to a,(i-unsaturated ketones is also catalyzed by the lanthanoid catalysts, leading to the formation of the corresponding epoxides with up to 96% ee (Scheme 8D.19) [41]. This reaction shall be reviewed in another chapter. 

The Michael addition of oxygen nucleophiles to vinyl sulfones185 and the addition of dimethyl malonate and ethyl cyanoacetate to a,fl-unsaturated sulfones in the presence of Triton-B and K2CO3 have been studied.186... 

In the Au(I) catalysis of electron-poor alkynes such as 4, the catalytically active species is likely to be a cationic ligand-stabilized gold(I) Jt-complex, as in previously reported additions of oxygen nucleophiles to alkynes [5], Gold catalysts are very soft and thus carbophilic rather than oxophilic. On the basis of this assumption a plausible mechanism can be formulated as shown in Scheme 6. The cationic or strongly polarized neutral Au(I)-catalyst coordinates to the alkyne, and nucleophilic attack of the electron-rich arene from the opposite side leads to the formation of a vinyl-gold intermediate 7 which is stereospecifically protonated with final formation of the Z-olefm 8 [2, 4]. Regioselectivity is dominated by elec-... 

Gold(III)-catalyzed addition of oxygen nucleophiles to alkynes ... 

Gold(I)-catalyzed addition of oxygen nucleophiles to alkynes (h) J. H. Teles, S. Brode,... 

The activating effect of Pd and Fe° toward nucleophilic addition to alkenes is powerful and allows addition of stabilized anions to simple alkenes at low temperatures. However, the only efficient catalytic processes are based on the addition of oxygen nucleophiles to alkenes activated by spontaneous coordination with Pd extensions of the Wacker process. 

These reactions are solvomercurations when the participating nucleophile is a part of the solvent. The terms oxymercuration for addition of oxygen nucleophiles, aminomer-curation for addition of amines, peroxymercuration for addition of OjH or OjR, etc., are used. 

Nucleophilic addition of oxygen nucleophiles formation of hydrates and acetals... 

Intramolecular cyclization of alcohols to 1,3-dienes can lead to fused tetrahydrofurans and tetrahydropyrans. In this reaction, using 5 mol% Pd(0Ac)2, the first step involves a trans oxypalladation to form the heterocyclic ring and a jr-allyl palladium complex. In the presence of 0.2 equiv. of LiCl, AcO adds trans to the r-allyl, leading to a net cA-l,4 addition of oxygen nucleophiles to the diene. When LiCl is omitted, the AcO adds to the same face of the r-allyl as the palladium, giving net tra/ 5-1,4-addition of oxygen groups to the diene (Scheme 41). 

Abstract Progress in the field of metal-catalyzed redox-neutral additions of oxygen nucleophiles (water, alcohols, carboxylic acids, and others) to alkenes, alkynes, and allenes between 2001 and 2009 is critically reviewed. Major advances in reaction chemistry include development of chiral Lewis acid catalyzed asymmetric oxa-Michael additions and Lewis-acid catalyzed hydro-alkoxylations of nonacti-vated olefins, as well as further development of Markovnikov-selective cationic gold complex-catalyzed additions of alcohols or water to alkynes and allenes. 

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