Epoxy-diene

Chain Diene Epoxymonoene Triene Epoxy diene ... 

The results of dT/dt and T measurements made during curing of two systems - macro(di-isocyanate) based on poly(tetraethylene glycol) and 2,4-toluylene diisocyanate cured by diamine (MDA) and epoxy diene oligomer cured by triethanol(amine titanate) are shown in Figs. 3.9 and 3.10, respectively. The monotonic increase in the parameters, monitored in the experiment,... 

The ionone series of compounds has been fruitful for Jeger smd his coworkers. The area is clearly not exhausted and they have studied the behaviour of the epoxy dienes (93) under acetone-sensitized irradiation. Irradiation of the enol benzoate (94) in the presence of acid yields the isoquinolinone (95) in good yield by a mechanism involving cyclization, elimination and oxidation. ... 

In a study of methods of leukotriene synthesis, Ernest and co-workers discovered that triphenylphosphoranylidene-crotonaldehyde 5 reacts with the epoxyaldehyde 6 to give a 1 4 mixture of the key leukotriene A4 intermediate (E. -epoxy diene aldehyde 1 together with the novel (Z, )-epoxydiene aldehyde 8 (Scheme 5.3). The availability of 8 made possible the preparation of (7,11,14Z,9 )-LTA4 (9) and (7,11,14Z,9 )-LTD4 (10) (about IMO as active as LTD4 as a contractile agonist on guinea pig ileum tissue). 

Cyclization of epoxy dienes. Corey and Sodeoka have examined in detail the optimum conditions for cyclization of the epoxydiene 1. Of several Lewis acids, CH3AICI2 was found to increase the rate of cyclization more than (CH3)2A1C1 or (CH3)2A10Tf, but the yield was comparable in all cases. Methylene chloride is superior to CICH2CH2CI, CH3NO2, or toluene as solvent. Under optimal conditions the cyclization was carried out at —78° for 1 hour followed by silylation. The principal products are the silyloxy ketone 2 and the monocyclic silyloxy methyl ketone 3, formed under all conditions as a minor product... 

Figure 2. Diagnostic fragment ions in the mass spectra of (A) dienes trienes, (B) epaxymonoenes, and (C) epoxy dienes.

Fig. 43 Temperature dependencies of mechanical loss tangent for epoxy-diene networks. Numbers of curves correspond to (1) 19.6% of epoxy blocks, (2) 31.4%, (3) 46.6% [243]...

The steroidal 4/3-acetoxy-5/J,6/l/-epoxy-2-en-l-one system 546 was converted at room temperature into the 6/3-hydroxy-2,4-dien-l-one 547 by reductive elimination of the vicinal oxygen function, and the reaction has been applied to the synthesis of withanolide[352]. 

A solution of 17-cyanoandrosta-5,16-dien-3jS-ol acetate (46 g) and anhydrous potassium acetate (0.46 g) in methylene dichloride (310 ml) is treated with a mixture of 40% peracetic acid (37 ml) and anhydrous potassium acetate (1.84 g) in methylene dichloride (46 ml), the temperature of the solution being maintained below 25°. The mixture is stored at room temperature for 4 hr and then washed successively with water, 5% sodium bicarbonate solution (aqueous sodium bisulfite, 10g/150g water, has been used to decompose excess reagent before workup) and water until neutral. Evaporation of the dried solution and addition of ether gives 24.1 g of 5oc,6a-epoxy-17-cyanoandrost-16-en-3 -ol acetate mp 187-190°. One recrystallization from methanol gives 20.4 g of oxirane melting at 191-194°. 

Enolate trapping, 97 Epoxidation of steroidal dienes, 7 Epoxidation of steroidal monoenes, 2 4, 5/3-Epoxycholestan-3 -ol, 27 5a,6a-Epoxy-5a-cholestan-3 -ol, 82 5a,6a-Epoxy- 17-cy anoandr ost-16-en-3 jS-ol acetate, 20... 

Enantioselective epoxidation of unfunctionalized alkenes was until recently limited to certain ds-alkenes, but most types of alkenes can now be successfully epoxi-dized with sugar-derived dioxiranes (see Section 9.1.1.1) [2]. Selective monoepox-idation of dienes has thus become a fast route to vinylepoxides. Functionalized dienes, such as dienones, can be epoxidized with excellent enantioselectivities (see Section 9.1.2). 

Cleavage of carbonyl-containing selenoxides and sulfones Fragmentation of epoxy hydrazones Rearrangement of vinylic hydroxycyclopropanes Rearrangement of 3-hydroxy-1,5-dienes (oxy-Cope)... 

CN (5Z,9a, 11 a, 137 , 155)-6,9-epoxy-11,15-dihydroxy-prosta-5,13-dien-1 -oic acid monosodium salt... 

Diels-Alder reactions provide one of the few general methods of forming two carbon-carbon bonds simultaneously. The main features of these reactions are described in Box 1.3. The reaction finds widespread industrial use for example hardeners for epoxy resins are made by reaction of maleic anhydride with dienes such as 2-methyl-1,4-butadiene. 

On a capillary GC analysis, the separation of positional isomers of epoxy compounds is generally well accomplished by a high polar column, such as DB-23, rather than by a low polar column, such as DB-1. For the positional isomers, a different elution order depending on the kinds of column has not been reported. In the case of two mono epoxides derived from Z6,Z9-dienes, 6,7-epoxides elute slightly faster than 9,10-epoxides [72,170],but the separation is insufficient even on the high polar column. Three monoepoxides derived from Z3,Z6,Z9-trienes elute in the order of 6,7-, 3,4-, and 9,10-epoxides [9]. The former two isomers are sufficiently separated on the high polar column, while the elution of the latter two isomers overlaps [71]. For each positional isomer of diepoxides derived from the Z3,Z6,Z9-trienes, two diastereomeric... 

In parallel investigations, Danishefsky and coworkers accomplished the preparation of the 16-membered lactone of a model epothilone system via an alternative C9,C10 disconnection [14] (Scheme 4). In this case, coupling of epoxy-alcohol 17 with acids 18a and 18b afforded trienes 19a and 19b respectively. RCM of 19a under the influence of ruthenium initiator 3 produced dienes 20a as a 1 1 mixture of Z -isomers. Under identical conditions, cyclization of 19b produced a single product 20b (tentatively assigned as the Z-isomer). The variable stereoselectivity observed in these reactions was inconsequential since the olefinic functionality could be reduced to afford the corresponding saturated macrolactones. Schrock s molybdenum initiator 1 promoted the cyclization of 19a and 19b with similar efficacy [14]. 

When the epoxy-isobutenyl ester of crotonic acid is treated with the Cp2ZrCl2/AgC104 Lewis acid, the epoxide is opened by intramolecular assistance of the ester carbonyl group, giving a dioxolenium cation (Scheme 8.49). This species is a highly electrophilic Diels—Alder dienophile that reacts with a range of dienes. THF deactivates cationic zirconocene species and is therefore not tolerated as a solvent [89]. 

Hydroxy epoxidation of dienes.2 Photosensitized oxygenation of dienes when catalyzed by titanium(IV) isopropoxide results in an epoxy alcohol, formed by an oxygen transfer from an allylic hydroperoxide. 

Scheme 26 Synthesis of (3R,5 )-2,6-dimethyl-2,3-epoxy-octa-5,7-diene, isolated from male Amblypelta nitida [121]...

Fig. 10.24. Simplified metabolism of buta-1,3-diene (10.101), showing the formation of reactive metabolites bearing an epoxy group (i.e., 10.102, 10.103, and 10.105) or an a,(5-unsatu-rated carbonyl moiety (e.g., 10.109 and 10.110)...

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