Diepoxidation

The use of hydroxyethyl (also hydroxypropyl) methacrylate as a monomer permits the introduction of reactive hydroxyl groups into the copolymers. This offers the possibility for subsequent cross-linking with an HO-reactive difunctional agent (diisocyanate, diepoxide, or melamine-formaldehyde resin). Hydroxyl groups promote adhesion to polar substrates. 

Bisphenol A diglycidyl ether [1675-54-3] reacts readily with methacrylic acid [71-49-4] in the presence of benzyl dimethyl amine catalyst to produce bisphenol epoxy dimethacrylate resins known commercially as vinyl esters. The resins display beneficial tensile properties that provide enhanced stmctural performance, especially in filament-wound glass-reinforced composites. The resins can be modified extensively to alter properties by extending the diepoxide with bisphenol A, phenol novolak, or carboxyl-terrninated mbbers. 

Other examples of DAP copolymerizations of industrial interest include copolymerization with MMA in emulsion (50) and for light focusing rods (51) with vinyl naphthalene for lenses (52) with epoxy acrylates and glass fibers (53) epoxy acrylates and coatings (54) with diacetone acrylamide (55) with ahphatic diepoxide compounds (56) triaHyl cyanurate in lacquers for printed circuits (57) and DAIP with MMA (58). 

Oxidation of aHoocimene in the presence of a catalyst produces a polymeric peroxide, which can be thermally isomerized to produce aHoocimene diepoxide [3765-28 ] (56) in 70—75% yield (99). The diepoxide has been used in the manufacture of resins and as an acid scavenger for halogenated solvents (100). 

Butadiene can also be readily epoxidized with peracids to the monoepoxide or the diepoxide (109,110). These have been proposed as important intermediates in the metaboHc cycle of butadiene in the human body (111). 

Exposure studies have been made using mice and rats (257). These experiments have demonstrated species differences in butadiene toxicity and carcinogenicity. Butadiene was found to be a potent carcinogen in the mouse, but only a weak carcinogen in the rat. The interpretations have focused on differences in toxification rates and detoxification metaboHsms as causative factors (257). The metaboHsm is beHeved to proceed through intermediates involving butadiene monoepoxide and butadiene diepoxide (257). A similar mechanism has been proposed for its biodegradation pathway (258). 

Group IV substituted, 1, 614-620 Cyclopentadiene-spiropyrazolenine photolysis, 5, 251 Cyclopentadienone, 2,3-epoxy-photochromic compound, 1, 385 Cyclopentadienone, tetraphenyl-diepoxide, 7, 191... 

Higher moleeular weight products may be obtained by reducing the amount of excess epichlorohydrin and reacting the more strongly alkaline conditions which favour reaction of the epoxide groups with bis-phenol A. If the diglycidyl ether is considered as a diepoxide and represented as... 

These materials differ from the previous class of resin in that the basic structure of these molecules consists of long chains whereas the cyclic aliphatics contain ring structures. Three subgroups may be distinguished, epoxidised diene polymers, epoxidised oils, and polyglycol diepoxides. 

The polyglycol diepoxides, which are used as reactive flexibilisers, are considered in the next section. 

More interest has been shown in polymeric flexibilisers, particularly the low molecular weight polyamides from dimer acid (see Chapter 18), the low molecular weight poly sulphides (Chapter 19), polyamines and the polyglycol diepoxides. 

Yet another approach to the production of flexible epoxide resin-based systems is to modify the epoxide resin itself. There are now available polyglycol diepoxides of the general strueture in Figure 26.22 where n is in the range 2-7. 

A terminal 1,13 diene with interstitial deka(difluoromethylene) chain is converted to the corresponding diepoxide by repeated reacUon with a very large excess of hypofluorous acid-acetonitrile complex [22](equation 14)... 

Nonconjugated perfluorocyclohepta-l,4-diene is oxidized to the corresponding diepoxide by sodium hypobromite [17] (equation 36), whereas the conjugated- 1,3-diene gives a mixture of 1,2-monoepoxide and bridged 2,3 1,4-diepox-ide [IT] (equation 36). 

Show the structure of the polymer that results from heating the following diepoxide and diamine ... 

When the diepoxide of norbornadien-7-one is passed through a hot capillary tube with nitrogen, a small amount (20 %) of oxepin is formed in addition to 4,5-epoxy-4,5-dihydrooxepin... 

In the synthesis of the bromo derivative 12 from diepoxide 11, an interesting epoxide ring-opening-ring-closure reaction is involved.5... 

Tandem 5-exo-oxacyclizations of polyepoxides to form polycyclic ethers are well known. In Evans s synthesis of lonomycin A, diepoxide 66 underwent the desired... 

In another interesting application of this procedure, the acid-mediated cascade cyclization of (3-diketone diepoxide 73 involves the participation not only of the two oxirane rings and of the secondary alcoholic group, but also of one of the two carbonyl groups. In this way, besides the two adjacent C and D THF rings, the simultaneous construction of the spiroketal function between the B and C rings of etheromycin is obtained (compound 74, in a 70 30 mixture with 12 -epi compound Scheme 8.19) [37]. 

Similarly, in another example, alkylation of 111 with diepoxide (—)-115 (1 equiv.) in the presence of HMPA (1.3 equiv.) furnished diol (+)-117. Protection of (+)-117 to form the acetonide, removal of the silyl protecting groups (TBAF), and hydrolysis of the dithiane with Hg(Cl04)2 provided the diketone (+)-118. Hydroxy-directed syn-reduction of both carbonyl groups with NaBI U in the presence of Et2BOMe, and triacetonide formation, followed by hydrogenolysis and monosilylation, afforded the desired Schreiber subtarget (+)-119, which was employed in the synthesis of (+)-mycoticins A and B (Scheme 8.31) [56b]. 

Epoxidation of conjugated dienes can be regioselective when one double bond is more electron-rich than the other otherwise mixtures of mono- and diepoxides will be obtained. When the alkene contains an adjacent stereocenter, the epoxidation can be diastereoselective [2]. Hydroxy groups can function as directing groups, causing the epoxidation to take place syn to the alcohol [2, 3]. 

Scheme 12.9 Reactions of cydohexadiene diepoxides with amines [2].

Through the same three-step sequence the analogous ris-diepoxide 10 [33] gave the related lactone 11, identical to 9 except that the two B-ring substituents have switched positions. All steps for both sequences proceeded in excellent yield. 

---