Tosylates reactions with carbonyl compounds

Elimination. ( , )-1,3-Dienamines are obtained from (Z)-4-methoxy-2-aIkenyl-amines by treatment with BuLi (or NaHMDS). Elimination of MeOH is stereoselective. A preparation of trifluoromethylallenes from l,l-dichloro-3,3,3-trifluoropropen-2-yl tosylate involves treatment with BuLi to generate lithium 3,3,3-trifluoropropynide, which is used for reaction with carbonyl compounds and then Negishi coupling. ... 

Various [l- C]carboxylic acids have been prepared by carboxylation of carbanions stabilized by -I or -M substituents. The examples in Figure 5.7 have been selected here as prototypes, since they are of strategic interest. Deprotonation of diethyl methylphos-phonate (18 with n-BuLi followed by [ CJcarboxylation and esterification with diazoethane provided triethyl phosphonoll- Clacetate (19) in an overall radiochemical yield of 62%. Compound 19 has been widely exploited for chain extensions by a labeled two-carbon unit via its alkenylation reaction with carbonyl compounds (Homer-Wadsworth-Emmons reaction). Similarly, reaction of alkyl halides, tosylates or carbonyl compounds with LiC = CH or LiC=CH H2NCH2CH2NH2 followed by deprotonation and [ C]carboxylation of the resulting terminal alkynes has been used as a strategic tool for the incorporation of a labeled three-carbon unit, as exemphfied in a steroid platform (20 to 21). This chemistry provides outcomes complementary to those using [ C2]acetylene (Chapter 8, Section 5.1). Finally, the [ CJcarboxylation of lithiated dimethylsulfide provided an alkylthio[l- C]acetic acid 22 and thence a functionalized 2-alkylthio[l- C]ethyl derivative 23 useful, in this case, for elaboration into e.p. 

Difluoro-l-(tosyloxy)vinyllithium 586 has been employed as an acyl anion equivalent of the type 587. This anion was prepared by treatment of 2,2,2-trifluoroethyl tosylate with two equiv of LDA at —78 °C860 (Scheme 159). The reaction of intermediate 586 with carbonyl compounds, followed by acid hydrolysis, gave compounds 588 which, after basic treatment with sodium hydroxide, afforded ct-keto acids 589. The reaction of the intermediate 586 with boranes provided the corresponding borates, which have been used in the synthesis of fluorinated molecules861. 

Although the formation of three-membered rings by cyclopropanation of olefins with metal carbenoids is commonplace, the construction of such systems via intramolecular C-H insertion is quite rare. This is because 1,2 migration of any hydride atoms a to the carbenoid center is typically very facile, rendering it inactive toward further transformations [56], It was found, however, that [i-tosyl a-diazo carbonyl compounds 37 are suitable substrates for intramolecular 1,3 C-H insertion reactions catalyzed by achiral rhodium carboxylates 25 (Scheme 6) [57],... 

N-tosylimino-oxysulphurane. This ylide reacts in high yield with carbonyl compounds to afford oxirans in a reaction analogous to that effected by sulphonium or oxysulphonium ylides. Optically active phenylmethylsul-phoximine could be tosylated and converted into an ylide with sodium hydride in DMSO, and it reacted with acetophenone to afford optically active 1-phenyl-1-methyloxiran. The ylide (156 R = R = Me) also effected additions to conjugated carbonyl compounds, such as co-benzoylstyrene, to afford l-phenyl-2-benzoylcyclopropane. Johnson recently has reviewed the use of N-tosyliminosulphoxonium ylides in organic synthesis. 

Benzene hydrocarbons are known to undergo radical coupling reactions and the intramolecular reductive coupling of carbonyl compounds with a benzene ring has been achieved. Best conditions for this process are at a tin cathode with isopropanol solvent and tetaethylammonium tosylate as supporting electrolyte [102, 103], The reaction is performed at constant current in a divided cell. A single stereoiso-... 

Tertiary amines are oxidized to the corresponding nitrogen oxides. Tosyl hydrazones of ketones and aldehydes and imines are oxidized to the corresponding carbonyl compounds. Reactions have been carried out with small molecules and also with molecules that would not diffuse into the pore structure of the titanium silicates. As in the case of C—C bond cleavage, it is possible that these reactions take place on the outer surface of the catalyst crystals. 

Toluene p-sulfonyl hydrazones (tosyl hydrazones) undergo C=N oxidative bond cleavage with H202 in the presence of TS-1, to give high yields of the corresponding carbonyl compounds very likely, the reaction proceeds through... 

A 2-cyclohexenone derivative can be transformed into the corresponding epoxy tosyl-hydrazone by sequential treatment with peracid and tosylhydrazine. The elimination of nitrogen and p-toluenesulfinate and fragmentation after rearrangement to the 3-tosylazo allylic alcohol may occur under mild conditions. Carbonyl compounds with 5,6-triple bonds are formed in high yields (J. Schreiber, 1967 M. Tanabe, 1967). If one applies this reaction to a 9,10-epoxy-1-decalone, a ten-membered 5-cyclodecyn-l-one ring is formed (D. Felix, 1971). This product is an important intermediate in the perfume industry and has been used on a large scale. For this purpose Eschenmoser developed a synthesis in which the readily removed styrene was split off instead of a sulfmic acid. Thus a l-amino-2-phenylaziridine hydrazone was used instead of a tosylhydrazone (D. Felix, 1968). ... 

The ring opening of enantiopure IV-tosyl aziridines 215 with 2-substituted 2-lithio-l,3-dithianes takes place at the less substituted carbon atom in good yields (59-92%)321. The corresponding adducts gave /9-tosylamino carbonyl compounds after reaction with methyl iodide under acetone reflux. 

Derivatives of 1-methyl-3//-l,4-benzodiazepine-2,5(l/I,4/I)dione (193) were synthesized by ring closure of substituted 2-(A-chloro-acetyl-A-methylaminoJbenzamides with sodium methoxide in methanol.209 Treatment of 193 with lithium aluminum hydride led to reduction of both carbonyl groups.209 The parent tetrahydro system (194) has been prepared by reaction of the tosylate (195) with 1,2-dibromoethane followed by hydrolysis.210 The preparation of 194 by another route had previously been noted.204 Reaction of 194 with formaldehyde or benzaldehyde gave a compound formulated as 196 (R = H or C6H5).210 Hydrolysis of 196 (R = C6H5) with 0.1 N hydrochloric acid gave 194 while 196 (R = H) was not hydrolyzed at this acidity. 

Oxidative cleavage of hydrazones. Carbonyl compounds can be regenerated from 2,4-dinitrophenylhydrazones, tosylhydrazones, or N-methyl-N-tosylhydra-zones in 80-95% yield by oxidation with sodium nitrite in TFA or HOAc (0-5°, 1-2 hours). In the case of tosylhydrazones, the other product of cleavage has been identified as tosyl azide, the product of reaction of tosylhydrazine with nitrous acid. 

Dialkyl 1-alkynylphosphonates (22) were formed in good to high yields by treatment of 1-alkynyliodonium tosylates (23) with trialkyl phosphites the reaction is exothermic with trimethyl phosphite but requires heating with triethyl or triisopropyl phosphite. The addition of trimethyl or triethyl phosphite to 3-alkylene-2-oxindoles (24) has led to new product types for a, -unsaturated carbonyl compounds, i.e. a stable tri-alkoxyphosphonium zwitterion (25), and a C-alkylated phosphonate (26). ... 

With alkyl halide substrates, the first step of the oxidation is the Sn2 displacement of the halide with tosylate anion. Next the alkyl tosylate undergoes a second Sn2 reaction with the nucleophilic oxygen atom of the DMSO to form the alkoxysulfonium salt that undergoes deprotonation to give the alkoxysulfonium ylide, which upon a [2,3]-sigmatropic shift affords the carbonyl compound. In the case of a-halo carbonyl substrates, the deprotonation takes place at the more acidic a-carbon instead of the methyl group attached to the sulfur atom of the alkoxysulfonium salt. 

The 2,3-dihydro-l//-pyrazole obtained from the reaction of hydrazine with an a-)8-unsaturated carbonyl compound will sometimes give a sufficient proportion of the 4,5-dihydro-3i/-pyrazole tautomer at equilibrium so that it is possible just to heat the 1//-tautomer to eliminate nitrogen and form a cyclopropane. In other cases, it is necessary to reduce the 1//-tautomer and oxidize back to the 3 -form. It is also possible to use the conversion of the H- to the 3//-tautomer to introduce substituents at C3 of the 4,5-dihydro-3//-pyrazole and hence into the cyclopropane. The reaction of 4-methylpent-3-en-2-one with hydrazine gave 2,2,4-trimethyl-2,3-dihydro-lH-pyrazole (1). Treatment with lead tetraacetate gave the 3-acetoxy derivative 2 and on thermolysis, l-acetoxy-l,2,2-trimethylcyclopropane (3). Alternatively, tosylation and reaction with methyllithium gave 3,3,5,5-tetramethyl-4,5-dihydro-3//-pyrazole (4) which on thermolysis or photolysis gave 1,1,2,2-tetramethylcyclopropane route to tetramethylcy-... 

A MW-assisted protocol for the synthesis of azides, thiocyanates, and sulfones has been developed (Scheme 12) that has proved to be a useful alternative, as the use of environmentally deterimental volatile chlorinated hydrocarbons is avoided.All the reactions with these readily available halides or tosylates have shown significant increase in reactivity, thus reducing the reaction times with substantial improvement in the yields. Various functional groups such as ester, carboxylic acid, carbonyl, and hydroxyl were unaffected under the mild reaction conditions employed. This method involves simple experimental procedures and product isolation which avoids the use of phase-transfer catalysts, and is expected to contribute to the development of greener strategy for the preparation of various azides, thiocyanates, sulfones, and other useful compounds. 

During the last years the reaction of 0-sulfonylated oximes with amines was applied repeatedly.It gives diaziridines even from electron-poor carbonyl compounds, which had not been accessible so far. For example, diaziridine 91 is obtained from the 0-tosyl oxime of mesoxalic ester (90). ... 

One of the major problems encountered in this synthesis is the difficulty of obtaining the starting materials (either the a-aminocarbonyl compounds or their acylated derivatives). The former may be prepared by Neber rearrangement of ketoxime tosylates with a base such as ethoxide or pyridine.46 a-Acylamino carbonyl compounds can be prepared directly by the reductive acetylation of oximino ketones.28 38 Balaban and his collaborators47-60 have developed an excellent method for the synthesis of a-acylamino ketones (5). They are obtained in yields of 50-90% by the reaction of azlactones (2-aryl-5-oxazolone, 4) with aromatic hydrocarbons in the presence of aluminum chloride under Friedel-Crafts conditions the reaction may proceed either intermolecularly or intramolecularly. 

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