Miscellaneous Enolates

The invaluable help rendered by Dr. (Miss) Saryu I. Davawala in the preparation of this manuscript is duly acknowledged. 

2 For reviews that include enolate Claisen rearrangement see a) Ziegler, F. E. Acc. Chem. Res. 1977, 10, 227-232. 

7 a) Wick, A. E. Felix, D. Steen, K. Eschenmoser, A. Helv. Chim. Acta 1964, 47, 2425-2429. b) Wick, A. E. Felix, D. Gschwend-Steen, K. Eschenmoser, A. Helv. Chim. Acta 1969, 52, 1030-1042. 

11 For the purpose of this article the simple enolate method is defined as the enolate having an alkali or an alkaline earth metal as a counterion. 

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Potassium ferricyanide, 255 of silyl enol ethers and lithium enolates Iodosylbenzene, 151 Miscellaneous methods Palladium catalysts, 230 Tetrakis(trifluoroacetate)ruthenium,... 

Miscellaneous Applications. Only one attempt to use (R)-pantolactone as an enantioselective protonating agent for enolates has been reported. A series of structurally diverse chiral alcohols afforded modest ee s with (R)-pantolactone affording the largest ee noted for the series. The complexities of attempting a proto-nation of this sort in the presence of base and under exchanging conditions are discussed. Finally, the lactone has been used to resolve chiral acids by crystallization and chromatographic techniques applied to the (R)-pantolactone-derived esters. - ... 

The following sections will discuss applications of Grignard reagents for metallation. The general categories are intramolecular rearrangements, enolates, and miscellaneous reactions. Eliminations are covered in a separate section. 

Miscellaneous. The phosphonium salt (92) has been shown to be an excellent reagent for the carboalkenylation of carbonyl compounds. For example, the sodium enolate (93) and (92) give a cyclic product (94) which is thought to arise from a stabilized ylide by cyclization via an intramolecular Wittig reaction. 

Miscellaneous Azides. Ethyl (A-methanesulfonyl)azidoformimidate [N3C (0Et)=NS02Me] has been used to aminate chiral cyclopentanone enamines but the yields are low and the reaction could not be extended to the corresponding cyclohexanone enamines.303 Trimethylsilyl azide (TMSN3) transfers the TMS rather than the azide group to a lactam enolate.339... 

Miscellaneous Reagents. Chloramine-T/Osmium Tetroxide. The Sharpless asymmetric aminohydroxylation system for olefins (4-MeC6H4S02N(Na)Cl/ OsCVcinchona alkaloid derived catalysts)340,341 converts silyl enol ethers into a-(p-tosylamino) ketones in 34-40% yield and 76-92% ee (see Eq. 99).342... 

Alkali Metal Enolates from Enol Acetates and Silyl Eru>l Ethers 1.423 Alkali Metal Enolates by Miscellaneous Methods... 

Miscellaneous. Acylation of unprotected amino acids, desilylation of TBS-ethers, alkylation of ketone enolates with (iso)/quinolinium salts, Wolff rearrangement, bromination of active arenes with NBS, and dichloroketene formation from Zn and CI3CCOCI (for cycloaddition to alkynes) have all been promoted with ultrasound. 

Additive in Miscellaneous Reactions. Concurrent addition of TMSCl and an enol trifiate into a preformed Boc-protected... 

Miscellaneous Reactions. Trimethylsilyldiazomethane converts acid- and base-sensitive maleic anhydride derivatives into the corresponding bis(methyl esters) (eq 70). Terminal silyl enol ethers are conveniently prepared from aldehydes by first treating the carbonyl compound with TMSC(Li)N2, followed sequentially by methanol and Rh2(OAc)4 (eq 71). The method works well with base-sensitive substrates and is superior to the attempted regioselective deprotonation/O-silylation of the corresponding methyl ketone. ... 

The Lewis acid-mediated coupling of alkyl enol ethers with acetals was discovered in 1937 by Martin Muller-Cunradi (1902-1945) and Kurt Pieroh at BASF, and is one of the lesser-known key reactions in the chemistry of carotenoids it can be employed in miscellaneous ways and repeatedly for the construction of complex structures. [64]... 

Dehydrosilylation coupled with miscellaneous synthesis of silyl enol ethers via rearrangement of 1-siloxy-l-alkenylcyclopropane/ reactions of y-siloxyaUylmetals with elec-trophiles/ and rearrangement of a-silylketones gives the corresponding ketones. 

Miscellaneous Reactions. Voelter and co-workers have observed the exclusive formation of the unexpected alkylation product 33, along with recovered starting material in their attempt to promote a [3 + 2] cycloaddition of 32 with Pd-TMM (eq 51). They speculated that either enolate formation or an electron-transfer process disrupt the expected [3 + 2] cycloaddition of 32 with Pd-TMM. 

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