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In the presence of chlorotrimethylsilane, trialkyl phosphite reacts smoothly with alkyl acrylates to give dialkyl 3-alkoxy-3-(trimethylsiloxy)-2-propenephosphonates in good yields.

Mass spectral fragmentation patterns of dimethylsilyl (DMS) ethers of primary unbranched, branched, and secondary unbranched aliphatic alcohols in the C5 to C10 range are compared with those of the corresponding trimethylsilyl (TMS) derivatives. Unlike their TMS analogues, DMS ethers of primary alcohols exhibit pronounced rupture of the CC bond adjacent to the oxygen atom within the alkyl moiety (loss of an alkyl radical R) in marked preference to cleavage within the silyl substituent (loss of CH3). Within this class of compounds, complementary preparation of DMS derivatives can therefore be used to establish or to confirm the site, and thus the primary nature of the hydroxyl group, whereas preparation of TMS ethers may be of advantage in deducing molecular size. For the derivatives of secondary alcohols this diagnostically useful difference in fragmentation behaviour is not observed.

1. The reaction of β-haloalkyl aryl sulfides or episulfonium salts with the trimethylsilyl ethers of enols is a general method for the introduction of the β-arylthioalkyl group into carbonyl compounds. 2. The opening of the episulfonium ring in this reaction is regioselective and stereospecific. 3. The reaction permits the synthesis of polyfunctional compounds from simple alkene and carbonyl compound precursors.

La lithiation se fait principalement en 1,10; reactions des composes lithies avec divers electrophiles

Alkyllithiums undergo trans addition to 3-(trimethylsilyl)-2-propyn-1-ols to yield (1-lithiovinyl)silanes. Due to unidentified side-reactions, yields do not exceed 20%

Nearly regular tetrahedral silicon bond configuration and a considerably distorted ring characterize the p -bis(trimethylsilyl)benzene molecular geometry according to an electron diffraction study. The SiC methyl bond is longer than the SiC phenyl bond, in agreement with expectation but contrary to an X-ray diffraction determination. The extent of ring deformation is consistent with the electropositive character of the trimethylsilyl substituent and with the structural variations in other para -disubstituted benzene derivatives. The electron diffraction data are consistent with either free rotation around the SiC phenyl bonds or with a rotamer deviating by about 15° from the eclipsed form. The following bond lengths ( r g , pm) and bond angles (°) have been determined with parenthesized estimated total errors: (CC) mean 140.8(3), (C ipso )(C ortho C meta ) 1.6(7), (SiC) mean 188.0(4), (SiC methyl )(SiC phenyl ) 3.3(7), (CH) methyl 111.3(3), CC ipso C 115.7(6), and C phenyl SiC methyl 109.2(4).

Ein 2:1-Gemisch aus Ozon und dem Diphosphen (I) ergibt bei tiefer Temperatur das relativ stabile Diperoxid (II), das mit Methanol zum Monoester (III) gespalten wird.

In contrast to the thermal stability of the oxido anions 7, facile eliminative rearrangement has been shown to occur in the case of the oxido anions 2 which possess an aryl substituent on the carbon atom bearing the trimethylsilyl group. Thus, the one-pot synthesis of the allyloxysilanes 5, starting from the (E)-β-(trimethylsilyl) vinyl sulfone 1, was achieved via the facile 1, 4-silyl rearrangement of the oxido anions 2 with concomitant loss of the benzenesulfonyl group.

Cristallisation dans le groupe P1 (Z=2, affinement jusqu'a R=0,037). La coordination autour de B est strictement plane. Les deux angles (Me 3 Si) 3 C-B-C(Ph) sont plus grands que C(Ph)-B-C(Ph) a cause de l'encombrement sterique des groupes Me 3 Si

(±)-2,5,12-Trihydroxy-1,2,3,4-tetrahydronaphthacene-6,11-dione-2-carboxylic acid was found to readily afford the racemic title compound by successive treatments with N,N′-carbonyldiimidazole and methylmagnesium bromide in the presence of trimethylsilyl triflate. The same reaction scheme could also furnish the optically pure title compound from the (R)-carboxylic acid produced by the optical resolution.

Alkylation of sodium cyclopentadienyl(tricarbonyl)metal— lates of tungsten and molybdenum with o—chloro ketones and c—chloro esters gives stable tungsten and molybdenum enolates (23a—23d). Similar alkylation of sodium pentacarbonylrhenate provides rhenium enolates 24. Compounds 23 lOse carbon monoxide and rearrange to 3—oxaallyl complexes 25 upon irradia— tion. Compounds 25 react with benzaldehyde to give transition metal aldolates (26), which may be converted into the silylated aldol (27) and the corres ponding metal chloride (28) upon reaction with trimethylsilyl chloride. Rhenium enolate 27 undergoes thermal aldol reaction with benzaldehyde and Buffers exchange of one carbonyl ligand upon being heated with triphenylphosphine. The resulting cia monophosphine complex (30) and compound 27 itself both react with triphenylphosphine in refluxing acet*nitrile to give complex 31, in which the enolate moiety has been transferred from rhenium to the nitrile function. Several schemes for establishing catalytic cycles based on the foregoing reactions are suggested. Since the first report of the aldol addition reaction in 1838 (ref. 1), enolate ions have occupied a position of singular importance in organic chemistry. A large fraction of the most general synthetic methods involve these important intermediates. Nevertheless, until about 30 years ago, there was little direct study of enolate ions s.e, since most reactions in which they are involved were carried out under protic conditions where enolates are formed only as transient intermediates. Obvious exceptions are the enolates derived from 13—dicarbonyl compounds, which may be prepared in alcoholic, or even in aqueous solutions. The situation began to change in 1949 and 1950 when Frostick and Hauser introduced diisopropylaminomagnesium bromide as a catalyst for the Claisen condensation (ref. 2) and Hamell and Levine reported the first use of lithium diiso— propylamide (LDA) for the same purpose (ref. 3). These strong bases have the useful property of being soluble in aprotic solvents such as ether and THF, and allow the stoichiometric production of enolate salts. The first report of a stoichiometrically formed enolate salt came from Dunnavant and Hauser, who prepared the enolate of ethyl acetate with lithium amide in ammonia and demonstrated that it reacts with aldehydes and ketones to give 3—hydroxy esters in low yield (ref. 4). The utility of such preformed enolate salts was graphically demonstrated by M. W. Rathke in an important paper published in 1970 (ref. 5). Rathke showed that the sodium enolate is unstable even at —78 0C, but that the lithium enolate, prepared with lithium biB (trimethylsilyl)amide in THF, is stable indefinitely at —78 °C, and that solutions of ethyl lithio— acetate react smoothly with aldehydes and ketones to give the corresponding aldols in high yield. In the last decade, we have seen an intense investigation of the preparation, structures, and chemical reactivity of preformed metal enolates. The reader is referred to several recent review articles for a more complete coverage of the field (ref. 6—11). A large part of this interest has revolved about the increasing importance of stereocontrol in organic synthesis. In this regard, there has been a great deal of success in understanding and using stereoselec— tive aldol addition (ref. 8, 9 & 11) and alkylation (ref. 10) reactions. In the context of the aldol reaction, two fundamentally different kinds of stereoselectivity are possible and have been investigated. In reactions

Hydrosilylation of 1,4-bis(trimethylsily)-1,3-butadiyne with platinum and rhodium catalyst proceeded stepwise to give first 2-silyl-1,4-bis(trimethylsilyl)-1-buten-3-ynes and then 1,3-disilyl-1,4-bis(trimethylsilyl)-1,2-butadienes in high yields.

Carbonyl addition compounds of diethyl trimethylsilyl phosphite (DTMSP) with aldehydes were converted, by treatment with lithium diisopropylamide (LDA) followed by the successive alkylation and alkaline hydrolysis, to carbonyl derivatives involving aldehydes, unsymmetrical ketones, β,γ-unsaturated ketones, and carboxylic acids. β-Substituted carboxylic esters and γ-substituted lactones were prepared by use of the carbonyl addition compounds of DTMSP with α,β-unsaturated aldehydes.