Epoxides with acid

The final resin product is obtained by reacting (curing or crosslinking) the above di-epoxide with acid anhydrides or polyamines. The curing agents (sometimes incorrectly called catalysts) react with the three-membered epoxide rings to produce a highly crosslinked polymer. 

The intermediate cation in a pinacol rearrangement can equally well be formed from an epoxide, and treating epoxides with acid, including Lewis acids such as MgBr2, promotes the same type of reaction. 

Araliopsine (62), which is present in Araliopsis soyauxii (J. Vaquette et al., Phytochem., 1975, 15, 743) and Zanthoxyllum simulans (z. Chang et al., Yaoxuc Xuebao, 1981, 16, 394 C.A., 1982, 97, 20735) has been synthesised by G.M. Coppola (J. heterocyclic Chem.,1983, 1589) by reacting N-methylisatoic anhydride with the lithium enolate (51) and treatment of the intermediate epoxide with acid. 

Treatment of manool with permanganate cleaves the side chain in the same way that it cleaves the side chain of sclareol. This gives the unsaturated ketone (8.43), as shown in Figure 8.12. Epoxidation of (8.43) gives the epoxide (8.44) as expected. Treatment of this epoxide with acid produces the ketal (8.45). This ketal is known as Jeger s ketal, after... 

The carbocation intermediate in a pinacol rearrangement could be stabilized by intramolecular electron donation from the adjacent hydroxyl group to form a protonated epoxide. Indeed, epoxides have, on occasion, been isolated under pinacol rearrangement conditions and have been implicated as intermediates as well. For example, when (-)-benzoin was treated with methylmagnesium iodide followed by dilute aeid, an optically-active epoxide was isolated. " Further treatment of the epoxide with acid generated a racemic ketone. 

Dimerization of the formed cx,P-hydroxy aldehyde may become a serious issue in the hydroformylation of epoxides with acidic metal catalysts. Orchin s group observed chiefly self-acetallzatlon products in the stoichiometric ring-opening reaction of cyclohexene oxide with CO and HCo(CO) (Scheme 6.108) [23]. 

Treatment of bicyclic epoxides with acid affords rearranged aldehydes. 

Haugan, J.-A. and Liaaen-Jensen, S. (1994b) Blue carotenoids. Part 2. The chemistry of the classical colour reaction of common carotenoid 5,6-epoxides with acids. Acta Chem. Scand., 48,152-159. 

Regioselectivity of C—C double bond formation can also be achieved in the reductiv or oxidative elimination of two functional groups from adjacent carbon atoms. Well estab llshed methods in synthesis include the reductive cleavage of cyclic thionocarbonates derivec from glycols (E.J. Corey, 1968 C W. Hartmann, 1972), the reduction of epoxides with Zn/Nal or of dihalides with metals, organometallic compounds, or Nal/acetone (seep.lS6f), and the oxidative decarboxylation of 1,2-dicarboxylic acids (C.A. Grob, 1958 S. Masamune, 1966 R.A. Sheldon, 1972) or their r-butyl peresters (E.N. Cain, 1969). 

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). 

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... 

Dieldrin [60-57-1] or l,2,3,4,10,10-hexachloro-l,4,4t ,5,8,8t -hexahydro-6,7-epoxy-l,4- <7o, Aro-5,8-dimethanonaphthalene (34) (mp 176°C, vp 0.4 mPa at 20°C) is formed from aldrin by epoxidation with peracetic or perben2oic acids. It is soluble in water to 27 / g/L. Aldrin and dieldrin have had extensive use as soil insecticides and for seed treatments. Dieldrin, which is very persistent, has had wide use to control migratory locusts, as a residual spray to control the Anopheles vectors of malaria, and to control tsetse flies. Because of environmental persistence and propensity for bio accumulation, registrations in the United States were canceled in 1974. 

Primary cycloaUphatic amines react with phosgene to form isocyanates. Reaction of isocyanates with primary and secondary amines forms ureas. Dehydration of ureas or dehydrosulfuri2ation of thioureas results in carhodiimides. The nucleophilicity that deterrnines rapid amine reactivity with acid chlorides and isocyanates also promotes epoxide ring opening to form hydroxyalkyl- and dihydroxyalkylaniines. Michael addition to acrylonitrile yields stable cyanoethylcycloalkylarnines. 

Hydrogen Sulfide andMercaptans. Hydrogen sulfide and propylene oxide react to produce l-mercapto-2-propanol and bis(2-hydroxypropyl) sulfide (69,70). Reaction of the epoxide with mercaptans yields 1-aLkylthio- or l-arylthio-2-propanol when basic catalysis is used (71). Acid catalysts produce a mixture of primary and secondary hydroxy products, but ia low yield (72). Suitable catalysts iaclude sodium hydroxide, sodium salts of the mercaptan, tetraaLkylammonium hydroxide, acidic 2eohtes, and sodium salts of an alkoxylated alcohol or mercaptan (26,69,70,73,74). 

Epoxidation of diliydromyrcenol gives an iatemiediate epoxide that can be hydrogenated to hydroxycitronellol. Treatment of the diol with acid can also give the a-,P-citroneUol and the a-citroneUol can be isomerized to the P-citroneUol (27) (110). The diol, hydroxycitronellol, is also useful for produciag hydroxycitroneUal, a lily-of-the-valley fragrance material. 

Maltol. Otsuka Chemical Co. in Japan has operated several electroorganic processes on a small commercial scale. It has used plate and frame and aimular cells at currents in the range of 4500—6000 A (133). The process for the synthesis of maltol [118-71 -8], a food additive and flavor enhancer, starts from furfural [98-01-1] (see Food additives Flavors and spices). The electrochemical step is the oxidation of a-methylfurfural to give a cycHc acetal. The remaining reaction sequence is acid-catalyzed ring expansion, epoxidation with hydrogen peroxide, and then acid-catalyzed rearrangement to yield maltol, ie ... 

Cycloaliphatic Epoxy Resins. This family of aUphatic, low viscosity epoxy resins consists of two principal varieties, cycloolefins epoxidized with peracetic acid and diglycidyl esters of cycHc dicarboxyhc acids. 

BZOSO2CF3, —78°, CH2CI2, a few minutes. With acid-semsitive substrates pyridine is used as a cosolvent. This reagent also reacts with ketals, epoxides, and aldehydes. ... 

As with the other non-glycidyl ether resins the absence of the ether oxygen near to the epoxide group results in low reactivity with amine hardemers whereas activity with acid anhydride proceeds at reasonable rates. 

The opening of epoxides with neighboring keto groups, accompanied by vinylogous jS-elimination, has already been mentioned (section V). This is an extension of the jS-elimination reactions which occur when a,p- or jS,y-epoxy ketones are opened with acid or base. a,jS-Epoxy ketones give a-substituted a,jS-unsaturated ketones [(162), for example], and j5,y-epoxy ketones give y-substituted a,jS-unsaturated ketones [(163), for example] ... 

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