Epoxy reactions with amide

The reaction of the epoxy group with the mercaptan ( as with an amine or amide group. 

Cure of epoxy with combinations of monomeric curing agents and the use of polymers containing reactive groups to cure epoxy systems is rarely touched upon in the literature and could be investigated much further. Amides, polyesters, polyethers etc. used to cure the epoxy network could lead to the creation of materials having interesting and heretofore unfathomed properties. The fundamental kinetics of the reactive polymer epoxy reaction is an area of interest as well. 

There are also several reactive diluents that do not contain epoxy groups. These are represented by triphenyl phosphite and y-butyrolactone (Fig. 6.7). The phosphite is a low-viscosity colorless liquid, which is sensitive to moisture. It reacts with hydroxyl groups in the resin. The y-butyrolactone is a very effective viscosity reducer. It can reduce the viscosity of a liquid DGEBA from about 15,000 to 2000 cP with only 10 pph. In the curing reaction with amines (Fig. 6.8), the lactone forms an amide, which can then crosslink with the polymer via the hydroxyl groups. 

Suitable curatives for the polysulfide-epoxy reaction include liquid aliphatic amines, liquid aliphatic amine adducts, solid amine adducts, liquid cycloaliphatic amines, liquid amide-amines, liquid aromatic amines, polyamides, and tertiary amines. Primary and secondary amines are preferred for thermal stability and low-temperature performance. Not all amines are completely compatible with polysulfide resins. The incompatible amines may require a three-part adhesive system. The liquid polysulfides are generally added to the liquid epoxy resin component because of possible compatibility problems. Optimum elevated-temperature performance is obtained with either an elevated-temperature cure or a postcure. 

So far the reactivity of epoxides has involved their use as an electrophile. However, oxtranyl anions can serve as functionalized nucleophiles in their own right. Thus, the sulfonyl substituted epoxide 107 can be deprotonated with -butyllithium to provide a stabilized anion which engages in facile Sn2 reaction with triflate 108 <03JOC9050>. Other examples of such stabilized epoxide anions include those derived from oxazolinyloxiranes (e.g., 110), which react with nitrones to provide the spirotricyclic heterocycles of type 112, Hydrolysis provides the epoxy amino acids 113, in which the carboxylic acid moiety was provided by the oxazoline nucleus and the amine functionality was derived from the nitrone <03OL2723>. A recent report has demonstrated that oxiranyl anions can also be stabilized by the amide functionality <03H(59)137>. 

Reaction with an a.-epoxy ketone. The reagent reacts with the epoxy ketone 1 to give the amide 2 in high yield. The product can be converted into 3-methyl-... 

The (S)-lactone acid 1, obtained from L-glutamic acid by nitrous acid deamination, was converted to the acid chloride, then treated with excess diazomethane followed by hydrogen iodide to yield the keto-lactone 2. Amidation occurred quantitatively to give the partially racemized amide 3, which was purified by repeated recrystallizations. The vicinal diol resulting from reaction with excess methylmagnesium iodide was protected as the acetonide 4. An isomeric mixture of olefins (Z , 26 74) was obtained from the subsequent Wittig reaction. Reduction followed by separation on silver nitrate coated silica gel gave the (Z)-and ( )-alcohols in 20% (6) and 61% (5) yield, respectively. Conversion of the (S)-( )-alcohol (5) to the chloride then afforded the thioether (7) on reaction with sodium phenylsulfide. The thio ether anion was formed by treatment with n-butyllithium. Alkylation with the allylic chloride" (8), followed by removal of sulfur, then yielded the diene 9, which was converted in several steps to (/ ) (-t-)-10,11 -epoxy famesol. 

Opening of a, -Epoxy Esters and Amides. Treatment of aromatic a,/3-epoxyamides with samarium iodide leads to the highly stereoselective synthesis of a./S-unsaturated amides with high diastereocontrol (eq 52). If the reaction is run on a substrate that contains y-protons, then a base-promoted reaction produces the (E)-a-hydroxy-, y-unsaturated amide (eq 53). ... 

Alkylated melamine-, urea-, and benzoguanamine-formaldehyde resins are the principal cross-linking agents in many industrially applied baked coatings. They are combined with acrylic, alkyd, epoxy, and polyester resins. The amide, hydroxyl, or carboxyl groups of these backbone polymers are used as functional sites for reaction with the amino resin. 

Fused 2-methylbutenolides have been prepared in good yield by the addition of 1-diethylaminopropyne to cyclic a-epoxy-ketones (Scheme 21). The intermediate unsaturated amide can by cyclized to the hydroxy derivatives (69) simply by treatment with acid. Alternatively, prior reaction with BF3 followed by acid leads to the unsaturated analogue (70), whereas final reduction with borohydride gives the... 

Only a relative few of the dozens of active hydrogen compounds that undergo reactions with the epoxy ring find widespread use in epoxy structural adhesives. The most common are amines, amides, acid anhydrides, phenols, thiols, and carboxylic acids. 

Scheme 5 Reaction of epoxy ethers with a chiral amide.

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