Epoxide alicyclic

Chiou and Letton (1992) examine the chemorheology of a complex industrial resin, Hercules 3501-6, containing a major epoxide (TGDDM), two minor epoxides (alicyclic diepoxy carboxylate and epoxy cresol novolac), a hardener (diaminodiphenyl sulfone, DDS) and a Lewis-base catalyst (boron trifluroride monoethylamine complex). They found that both the conventional WLF model (Equation (5.26)) (Ferry, 1980) and a modified WLF model (Equation (5.27) were appropriate to describe the chemorheology ... 

There are many types of epoxide resin the Atlas for the Coating Industry, produced by the Federation of Societies for Coating Technology, cites 47 IR spectra of different resins [77]. Some typical example structures are provided below for Novolac-type phenol (and Novolac-type o-cresol) epoxides, aromatic glycidyl ester-type epoxides, alicyclic epoxides (18-4), and polyalcohol glycidyl epoxides (polyglycol and polyol based). The IR spectra of some epoxides are show in Fig. 54. 

The reactions of diazomethane with heterocycles containing a ketonic grouping in the ring do not differ, in principle, from those of alicyclic ketones (see footnotes 3 and 177) ring expansion and the formation of epoxides compete. In general, ring expansion is the more important reaction for example, tetrahydropyran-4-one (99) is converted to l-oxacycloheptan-4-one (100) (60%) and 4,4 -epoxy-4-methyltetrahydropyran (101) (23%). ... 

Azibenzil, in the presence of 02 and Pd(OAc)2 or PdCl2 2 PhCN, forms an intermediate metal-oxygen-carbene complex which is able to epoxidize aliphatic and alicyclic olefins azibenzil itself is transformed into benzil75). 

Finally, it is important to mention that there are other related publications in which porphyrin macrocycles are not directly used as dipolarophiles but are transformed into new derivatives that can react with carbonyl ylides via ACE (alkene cyclobutene epoxide) reactions. This idea arose in 1997, when Russell and co-workers found that fused ester-activated cyclobutene epoxides 86 can be ring-opened to give carbonyl ylides 87, and that these can be trapped stereospecifically by ring-strained alicyclic dipolarophiles, such as 2,5-norbomadiene, to form hetero-bridged norbomanes 88 in good yields, through ACE transformations (Scheme 31) <97CC1023>. 

The chapter on alicyclic stereoselection has been splitted in two chapters (9 and 10). Chapter 10, which is exclusively devoted to Sharpless asymmetric epoxidation and dihydroxylation, has been rewritten de novo. The most recent advances in catalytic and stereoselective aldol reactions are incorporated in Chapter 9. 

During polymer chain growth, a back-biting process can lead to cyclic carbonate formation. In general, this process is more facile for aliphatic epoxides than for alicyclic epoxides and when the growing polymer chain dissociates from the metal center (Scheme 3). 

An interesting reversal of chiral induction in chromium(III)-salen complexes using a tartaric derived alicyclic diamine moiety (i.e., 7) has been observed by Mosset, Saalfrank, and co-workers <99T1063>. Thus, epoxidation of the chromene 8 using catalyst 7 and an oxidant consisting of MCPBA/NMO afforded the 3S,4S epoxide 9, whereas the Jacobsen catalyst (1) provided the corresponding 3R,4R enantiomer. A mechanistic rationalization for this curious crossover has not yet been proposed. 

Bacskai, R Polymerization of Alicyclic Epoxides with Aluminium Alkyl Catalysts. J. Polymer Sci. A 1, 2777 (1963). 

The relative reactivity of secondary and primary amines with epoxide, k2/kt, can affect the overall kinetics. If k2/kj is not close to 0.5 the parameter f in Eqs. (4-7) and (4-13) becomes significant. In this respect there are differences between aliphatic and aromatic or alicyclic amines. For the aliphatic amines the ratio k2/kj is reported to be in the range 0.6-0.7 83 90), whereas for aromatic amines values in the range 0.2 to 0.5 have been observed 90 9S). For the reaction of BADGE with DDS, Dobas et al. 94) reported a value of 0.21 for k2/k, at 80 °C. This factor is likely to account for part of the observed non-linearity in reduced rate plots at higher levels of conversion. 

Among the simple alicyclic epoxides known to undergo hydration readily )Sq. 631) are cyclobutene oxide, cydopentene oxide ami... 

Further evidence of the stereospecificity of this reaction lies in rcnulta secured with certain simple alicyclic epoxides (Eq. 378) such aa l-methyloyclchaxeoc oxide110 1107-114 and 1,2-dimethylcydohexene... 

In a similar manner, thiophonol has been condensed with etbyleno oxide itself,1230 with cyclohexene oxide,1230 and more recently with indene oxide.684 The last undergoes addition preferentially at the henscylic epoxide carbon atom Both alicyclic epoxides (Eqs. 663 and 664) are cleaved to 2-phenylthiocycloalkanols possessing fazna-con-figuration. 

Carboxylic ookl cleavage of ecmicyelie and alicyclic epoxides is amply exemplified in the literature. Oxidation of methyleneoyolo-hexane with perforraic acid, for example, yields a 1,2-diol mono-formate, from which may be obtained 1-hydroxymethylcyclohexanol... 

Perfluoroalkylated epoxides as representatives of alicyclic ethers are successfully oxidized152 directly to a-hydroxycarboxylic acids 5 despite the fact that the epoxides 4 are protonated and subsequently hydrolyzed with difficulty. It has been found that the tandem ring opening/oxi-dation reaction is accomplished by concentrated nitric acid152 in the presence of copper ions in the mixture.181... 

The photodecomposition of oxiran and alkyloxirans both in the gas phase and in solution has been extensively investigated. Processes arising by carbon-oxygen bond homolysis and hydrogen abstraction have been reported, and the subject has been reviewed in detail elsewhere.48 The most recent studies include the photoaddition of methanol to alicyclic epoxides, a process that appears to be promoted by acid,49 and the interesting if unusual photochemically induced conversion of the epoxyalcohol (56) to sugiresinol dimethyl ether (57).50... 

Most often, the extent of completely alternating copolymer formation, expressed as 100% C02 linkages or 50% C02 content, is very high. With regards to the selectivity of the coupling reaction for copolymer versus cyclic carbonate production, two observations are consistently found, regardless of the catalyst. First, aliphatic epoxides are more prone to cyclic carbonate formation than alicyclic epoxides for example, PO affords propylene carbonate more readily than CHO provides cyclohexene carbonate. Second, in either instance, since it has been shown that the activation barriers for cyclic carbonate production are higher... 

The alicyclic epoxide, limonene oxide, which is obtained from a renewable resource has shown modest activity compared to CHO for reaction with C02 to provide a copolymer. This significant decrease in reactivity is presumably due to the steric influence of a disubstitution at one of the ipso carbon centers. Of course, in either highly selective reaction, where complete formation of copolymer or cyclic carbonate occurs, the process displays 100% atom economy. The environmental attractiveness of this process is further enhanced by the fact that reactions are generally carried out in the absence of an organic cosolvent, that is, in C02-swollen epoxide solutions. 

Attempts to predict, from precedent, the behaviour of any particular alicyclic epoxide with a Lewis acid are complicated by the great diversity of known reactions. The best that can be done is first to consider the reaction of the epoxide in isolation as likely to lead to a ketone, unless special steric or conformational features interfere with the development of the necessary transition state. Consideration must then be given to inductive or electrostatic effects of any substituents in the vicinity of the epoxide, which may prevent ketone formation. 

Alkyaylailom aUeyeUe epoxuUs. Alkynyldiethyl alanes (2 eq.) react with alicyclic epoxides (1 eq.) to form, after hydrolysis, / -hydroxyacctylcnes in fair to excellent yields ... 

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