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Epoxides, preparation from

Quinidine, a natural product epimeric with quinine at Cg and C9, was accessed through the diastereoisomeric trans epoxide prepared from 86 by SAD, in this case by using AD-mix a [2b, 41]. [Pg.287]

Examples for straightforward epoxide preparation from natural sources can be found in carbohydrate chemistry [28,29]. Deoxygenations of such compounds are shown in Scheme 4. [Pg.39]

An inversion mechanism had been previously observed in the hydroxylation of caranine (2) to lycorine by Wildman and Heimer. They observed 7% incorporation of [2/ -3H] caranine into lycorine in Zephyranthes Candida Herb., the 3H being retained at C-2 of 1 as shown by the conversion into the inactive 385. The stereospecifically labeled precursor was obtained through LiAl3H4 reduction of lycorine-1,2-a-epoxide prepared from lycorine via its cis-chlorohydrin and chromatography on Florisil. The structure of the a-epoxide rests on physical and chemical grounds, whereas the stereochemistry of the... [Pg.148]

P = 1) systems while the apparent activation energy markedly decreases in the same series AEapp for the linear polymer DGER-AN is close to the typical value for many polymers 57 59). The results testify that the fragment (segment) of the network which is responsible for a-transition is in average smaller than that of a linear polymer. The temperature range of the T transition for the networks is markedly narrower than that for linear polymers and epoxides prepared from industrial resins 13,19). This points to a narrower distribution of relaxation times in the considered networks as compared with other crosslinked polymers. [Pg.75]

A double nucleophilic attack by benzylamine on a symmetric bis-epoxide, prepared from D-mannitol, was used in a recent synthesis of 250 [564], In another recent report, 5-keto-D-glucose was reacted with diphenylmethylamine and sodium cyanoborohydride in a key step in the formation of 250 [565]. [Pg.257]

The addition of aldehydes to carb - rCHN, to form stilbene epoxides prepared from 10-mercaptoisobc Jes derived from 48 on aldehydes i - -nciple underlies a synthesis of chn... [Pg.82]

To a mixture of 100 ml of THF and 0.10 mol of the epoxide (note 1) was added 0.5 g Of copper(I) bromide. A solution of phenylmagnesium bromide (prepared from 0.18 mol of bromobenzene, see Chapter II, Exp. 5) in 130 ml of THF was added drop-wise in 20 min at 20-30°C. After an additional 30 min the black reaction mixture was hydrolysed with a solution of 2 g of NaCN or KCN and 20 g of ammonium chloride in 150 ml of water. The aqueous layer was extracted three times with diethyl ether. The combined organic solutions were washed with water and dried over magnesium sulfate. The residue obtained after concentration of the solution in a water-pump vacuum was distilled through a short column, giving the allenic alcohol, b.p. 100°C/0.2 mmHg, n. 1.5705, in 75% yield. [Pg.172]

The regioselectivity of the addition of terminal alkynes to epoxides is improved, when the reagents prepared from the lithiated alkynes and either trifluoroborane or chlorodiethyl-aluminum arc employed (M. Yamaguchi, 1983 S. Danishefsky, 1976). (Ethoxyethynyl)lithium-trifluoroborane (1 1) is a convenient reagent for converting epoxides to y-lactones (M. Naka-tsuka, 1990 see p. 327f. cf. S. Danishefsky, 1976). [Pg.64]

The following section describes the preparation of epoxides by the base promoted ring closure of vicinal halohydrms Because vicinal halohydrms are customarily prepared from alkenes (Section 6 17) both methods—epoxidation using peroxy acids and ring closure of halohydrms—are based on alkenes as the starting materials for preparing epoxides... [Pg.676]

Esters. The monoisobutyrate ester of 2,2,4-trimethyl-1,3-pentanediol is prepared from isobutyraldehyde ia a Tishchenko reaction (58,59). Diesters, such as trimethylpentane dipelargonate (2,2,4-trimethylpentane 1,3-dinonanoate), are prepared by the reaction of 2 mol of the monocarboxyhc acid with 1 mol of the glycol at 150—200°C (60,61). The lower aUphatic carboxyHc acid diesters of trimethylpentanediol undergo pyrolysis to the corresponding ester of 2,2,4-trimethyl-3-penten-l-ol (62). These unsaturated esters reportedly can be epoxidized by peroxyacetic acid (63). [Pg.374]

Chlormadinone (38) is prepared from hydroxyprogesterone (39) by epoxidation and treatment of the epoxide with hydrochloric acid to provide the chloroalkene (40). Oxidation, ie, dehydrogenation, with chloranil, provides chlormadinone (38), which may be acetylated to provide chlormadinone acetate (63,64). [Pg.212]

Medroxyprogesterone acetate (74) is stmcturaHy related to and has been prepared from hydroxyprogesterone (39) (Fig. 10). Formation of the bis-ketal accomplishes the protection of the ketones and the required migration of the double bond. Epoxidation with peracetic acid produces a mixture of epoxides (75), with a predominating. Treatment of the a-epoxide with methyl magnesium bromide results in diaxial opening of the epoxide. Deprotection of the ketones provides (76), which is dehydrated to (77) by treatment with dilute sodium hydroxide in pyridine. Upon treatment with gaseous hydrochloric... [Pg.216]

Such copolymers of oxygen have been prepared from styrene, a-methylstyrene, indene, ketenes, butadiene, isoprene, l,l-diphen5iethylene, methyl methacrjiate, methyl acrylate, acrylonitrile, and vinyl chloride (44,66,109). 1,3-Dienes, such as butadiene, yield randomly distributed 1,2- and 1,4-copolymers. Oxygen pressure and olefin stmcture are important factors in these reactions for example, other products, eg, carbonyl compounds, epoxides, etc, can form at low oxygen pressures. Polymers possessing dialkyl peroxide moieties in the polymer backbone have also been prepared by base-catalyzed condensations of di(hydroxy-/ f2 -alkyl) peroxides with dibasic acid chlorides or bis(chloroformates) (110). [Pg.110]

Diarylamines do not react with carbon disulfide, whereas dialkylamines readily form dithiocarbamates. However, N,Ar-diaryldithiocarbamates can be prepared from metal salts of diarylamines and carbon disulfide (15). They are more stable than diaLkyldithiocarbarnic acids, eg, N,N -diphenyldithiocarbamic acid [7283-79-6] mp 142°C. Similarly, various metal salts of DPA react with carbon dioxide and an epoxide to give the P-hydroxyalkyldiphenylcarbamates (16). [Pg.243]

Other modifications of the polyamines include limited addition of alkylene oxide to yield the corresponding hydroxyalkyl derivatives (225) and cyanoethylation of DETA or TETA, usuaHy by reaction with acrylonitrile [107-13-1/, to give derivatives providing longer pot Hfe and better wetting of glass (226). Also included are ketimines, made by the reaction of EDA with acetone for example. These derivatives can also be hydrogenated, as in the case of the equimolar adducts of DETA and methyl isobutyl ketone [108-10-1] or methyl isoamyl ketone [110-12-3] (221 or used as is to provide moisture cure performance. Mannich bases prepared from a phenol, formaldehyde and a polyamine are also used, such as the hardener prepared from cresol, DETA, and formaldehyde (228). Other modifications of polyamines for use as epoxy hardeners include reaction with aldehydes (229), epoxidized fatty nitriles (230), aromatic monoisocyanates (231), or propylene sulfide [1072-43-1] (232). [Pg.47]

Dioxolanes haye been prepared from a carbonyl compound and an epoxide (e.g., ketone/SnC, CCI4, 20°, 4 h, 53% yield or aldehyde/ Et4N Br, 125-220°, 2-4 h, 20-85% yield ). Perhalo ketones can be protected by reaction with ethylene chlorohydrin under basic conditions (K2CO3, pentane, 25°, 2 h, 85% yield or NaOH, EtOH—H2O, 95% yield ). [Pg.191]

HDGS) upon exposure to a humid environment. As deseribed above, substrates were prepared by applying a phosphate eonversion eoating and then a ehromate rinse to HDGS. Lap joints were prepared from substrates having dimensions of 110 X 20 X 1.2 mm using a eommereial epoxide adhesive with a bond line thiekness of 250 (i.m. The joints were exposed to 95% RH at 35°C for 12 months and then pulled to failure. [Pg.306]

Is either of the epoxides formed in the preceding reactions chiral Is either epoxide optically active when prepared from the alkene by this method ... [Pg.678]

In addition, the cyclopentylidene ketal has been prepared from dimethoxy-cyclopentane, TsOH, CH3CN, or cyclopentanone (PTSA, CUSO4 >70% yield) and can be cleaved with 2 1 ACOH/H2O, rt, 2 h. Certain epoxides can be converted directly to cyclopentylidene derivatives as illustrated in the following reaction ... [Pg.216]

Due to the abundance of epoxides, they are ideal precursors for the preparation of P-amino alcohols. In one case, ring-opening of 2-methyl-oxirane (18) with methylamine resulted in l-methylamino-propan-2-ol (19), which was transformed to 1,2-dimethyl-aziridine (20) in 30-35% yield using the Wenker protocol. Interestingly, l-amino-3-buten-2-ol sulfate ester (23) was prepared from l-amino-3-buten-2-ol (22, a product of ammonia ring-opening of vinyl epoxide 21) and chlorosulfonic acid. Treatment of sulfate ester 23 with NaOH then led to aziridine 24. ... [Pg.65]

Deoxy-D-jcylo hexose 6-(dihydrogen phosphate) (21) has also been synthesized (2) the reaction sequence makes use of 3-deoxy l 2,5 6-di-O-isopropylidene D-galactofuranose (16), a compound that can be easily prepared from D-glucose (2, 60). The mono-isopropylidene derivative (17) formed by partial hydrolysis of the di-ketal is converted into the 6-tosylate (18) by reaction with one molar equivalent of p-toluenesulfonyl chloride. From this the epoxide (19) is formed by reaction with sodium methoxide. Treatment of the anhydro sugar with an aqueous solution of disodium hydrogen phosphate (26) leads to the 6-phosphate (20)... [Pg.80]

Easily prepared from the appropriate monosaccharide, a glycal is an unsatu-rated sugar with a C1-C2 double bond. To ready it for use in potysaccharide synthesis, the primary -OH group of the glycal is first protected at its primary -OH group by formation of a silvl ether (Section 17.8) and at its two adjacent secondary - OH groups by formation of a cyclic carbonate ester. Then, the protected glycal is epoxidized. [Pg.1002]

The optically active iodide 153 (Scheme 43) can be conveniently prepared from commercially available methyl (S)-(+)-3-hydroxy-2-methylpropionate (154) (see Scheme 41). At this stage of the synthesis, our plan called for the conversion of 153 to a nucleophilic organometallic species, with the hope that the latter would combine with epoxide 152. As matters transpired, we found that the mixed higher order cuprate reagent derived from 153 reacts in the desired and expected way with epoxide 152, affording alcohol 180 in 88% yield this regioselective union creates the C12-C13 bond of rapamycin. [Pg.608]

Hodgson et al. have demonstrated that arylalkenes 139 and dienes 140 can readily be prepared from simple terminal epoxides in a highly stereoselective manner by employing LTMP as base in combination with aryl and vinyllithiums as nucleophiles at 0 °C (Scheme 5.31) [41]. Without addition of LTMP, secondary alcohols... [Pg.160]


See other pages where Epoxides, preparation from is mentioned: [Pg.531]    [Pg.836]    [Pg.276]    [Pg.37]    [Pg.147]    [Pg.531]    [Pg.836]    [Pg.276]    [Pg.37]    [Pg.147]    [Pg.301]    [Pg.678]    [Pg.101]    [Pg.103]    [Pg.215]    [Pg.278]    [Pg.240]    [Pg.227]    [Pg.311]    [Pg.81]    [Pg.434]    [Pg.435]    [Pg.300]    [Pg.129]    [Pg.310]    [Pg.702]    [Pg.133]   


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Alcohols preparation from epoxides

Bromides, preparation from epoxides

Epoxide resins preparation from bis-phenol

Epoxides preparation

Epoxides preparation from alkenes

Epoxides preparation from halohydrins

Epoxides, preparation from aldehydes

Epoxides, preparation from tosyl alcohols

Ethers preparation from epoxides

From epoxides

Preparation cyclic carbonates from epoxides

Preparation epoxides from aldehydes using

Preparation of Alcohols from Epoxides

Selenides, preparation 1-hydroxy, from epoxides

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