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Rearrangement sulphonyl

Solanesol and other prenyl alcohols are important as metabolites in mulberry and tobacco leaves and in the synthesis of isoprenoid quinones. Hence, Sato and collaborators107 have developed a stereoselective synthesis of all-trans-polyprenol alcohols up to C50. Construction of the requisite skeletons was accomplished by the alkylation of a p-toluenesulphonyl-stabilized carbanion, followed by reductive desulphonylation of the resulting allylic sulphonyl group. This was achieved most efficiently by the use of a large excess of lithium metal in ethylamine (equation (43)), although all reaction conditions led to mixtures. The minor product results from double bond rearrangement. [Pg.945]

Despite the aversion of the sulphonyl group to function as a nucleophile, there are a limited number of literature reports that deseribe sueh a process . The first of these does not lead to a reduetion at sulphur and is thus not direetly relevant, but the report by Braverman and Duar deseribes reaetions in whieh an acetylenie sulphinate ester ean undergo a [2,3] sigmatropie rearrangement to an allenie t-butyl sulphone. Reaetion of this sulphone with the appropriate eleetrophile, for example bromine, gave a y-sultine, formation of whieh requires the partieipation of the sulphonyl group in an intramoleeular cyclization process. The reactions are outlined in equation (40). [Pg.943]

Starting materials other than sulphonyl azides have been used as possible sources of sulphonyl nitrenes. The decomposition of the triethyl-ammonium salt of iV- -nitrobenzenesulphonoxybenzenesulphonamide (26) in methanol, ethanol, and aniline gave products derived from a Lossen-type rearrangement 20> (Scheme 3). It was felt that the rearrangement did not involve a free sulphonyl nitrene since, when the decomposition was carried out in toluene-methylene chloride or in benzene, no products (benzenesulphonamides) of substitution of the aromatic solvent nucleus were found (as are usually found with sulphonyl nitrenes from the thermal decomposition of the corresponding azides). On the other... [Pg.16]

The chemical reactions of sulphonyl nitrenes include hydrogen abstraction, insertion into aliphatic C—H bonds, aromatic substitution , addition to olefinic double bonds, trapping reactions with suitable nucleophiles, and Wolff-type rearrangement. Hydrogen-abstraction from saturated carbon atoms is usually considered to be a reaction typical of triplet... [Pg.20]

When mesitylene-2-sulphonyl azide (3) is heated to 150 °C in n-dodecane, a Curtius-type rearrangement of the nitrene (4) occurs as discussed in Section 2.1 i to give 2,4,6-trimethylaniline and the hexa-methylazobenzene 14>. A similar result has now been observed by a careful analysis of the thermolysis products of durene-3-sulphonyl azide in w-dodecane at 150 °C. The amine is definitely formed but the azo-compound could barely be detected 13>. [Pg.34]

O-Substituted phenylhydroxylamines also undergo rearrangement to give the 2-isomers. For example O-(arenesulphonyl) phenylhydroxylamines 47 readily form the 2-sulphonyl derivatives 48. Experiments with 180-labelled compounds led to the suggestion54 of a mechanism involving an ion pair which has only a very short lifetime. [Pg.871]

The oxiranes obtained from the reaction of chloromethylsulphones with aldehydes and ketones can be isolated [26, 27], but tend to be unstable in the basic media. Rearrangement of the toluenesulphonyloxiranes produces the sulphonyl aldehydes (Scheme 6.15) [26]. When chiral chloromethylsulphonamides are used, asymmetric... [Pg.263]

Allylic phenyl tellurides are converted into the corresponding allylic amines by imination with [iV-(p-toluene-sulphonyl)imino] phenyliodinane. The reaction proceeds via [2,31-sigma-tropic rearrangement of a tellurimide intermediate. [Pg.202]

Amides are the least reactive of the carboxylic acid derivatives, and undergo acid or base hydrolysis to produce the parent carboxylic acids, and reduction to appropriate amines (see Section 4.3.10). They can also be dehydrated to nitriles, most commonly with boiling acetic anhydride, (AcO)20, sulphonyl chloride (SOCI2) or phosphoms oxychloride (POCI3) (see Section 4.3.18). Amines (with one less carbon) are prepared from amides by the treatment of halides (Br2 or CI2) in aqueous NaOH or KOH. This reaction is known as Hofmann rearrangement (see Section 4.3.10). [Pg.101]

The abnormal Beckmann rearrangement displayed by the oxime of 17-oxo-5a-androstan-3/3-yl acetate (248) to yield the 13,17-seco-nitrile (249) has provided the key step in a synthetic route to 17-oxo-18-nor-5a,13/8-androstan-3/S-yl acetate and its 13a-epimer.114 The reaction sequence is shown in Scheme 12. The 17-ketone (248) was converted via its oxime into the seco-nitrile in a yield of 52%. Treatment of the oxime by the more conventional toluene-p-sulphonyl chloride reagent... [Pg.311]

Beckmann rearrangements [43] of oximes of steroid ketones are quite normal in forming amides or lactams [44,43,46] unless special structural features interfere. Reactions are effected by the usual reagents, particularly thionyl chloride and sulphonyl chlorides. In one case the use of benzene- or toluene-j -sulphonyl chloride in a basic solution permitted the... [Pg.421]


See other pages where Rearrangement sulphonyl is mentioned: [Pg.488]    [Pg.491]    [Pg.499]    [Pg.503]    [Pg.504]    [Pg.506]    [Pg.943]    [Pg.201]    [Pg.9]    [Pg.11]    [Pg.33]    [Pg.375]    [Pg.6]    [Pg.18]    [Pg.18]    [Pg.154]    [Pg.274]    [Pg.97]    [Pg.201]    [Pg.115]    [Pg.43]    [Pg.310]    [Pg.784]    [Pg.215]    [Pg.215]   
See also in sourсe #XX -- [ Pg.98 , Pg.260 ]




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