Diene 2-ethoxy

The principal objection to -PDA antiozonants is their staining characteristics. The lack of suitable alternative antiozonants for light-colored diene mbber articles is one of the outstanding problems in mbber technology. Pew chemical antiozonants outside the class of -PDAs have much commercial importance. One of the few exceptions to this rule is 6-ethoxy-l,2-dihydro-2,2,4-trimethylquinoline [91-53-2] one of the first commercial antiozonants. 

The NMR spectra show that the product of the reaction contains the propyl group A of l-ethoxy-2-propylbuta-1,3-diene,... 

However, the ethoxy group of l-ethoxy-2-propylbuta-l,3-diene is no longer present. Evidently the p-toluensulphonyl eyanide (2) undergoes [4-1-2] eyeloaddition to l-ethoxy-2-propylbuta-l,3-diene (/). The resulting dihydropyridine 3 aromatises with 1,4-elimination of ethanol to form 2-p-lo y -sulphonyl-5-propylpyridine (4). 

M ethoxy-2,3,6-trimethylph enyl)-3-methy I penta-2,4-diene-1-triphenyl phos-phonium bromide Sodium hydride... 

To a Soiution of 3.0 g of 16/3-ethylestra-4-ene-3,17-dione dissoived in 150 ml of dioxane, are added 15 g of ethyl orthoformate and 0.1 g of p-toluenesuifonic acid, followed by stirring for 2 hours at room temperature. The reaction solution is poured into 300 ml of a 5% aqueous solution of Sodium hydrogen carbonate and the resultant mixture is extracted with ether. The ether layer is washed with water and dried, followed by evaporation of the solvent to give Crude crystals of 3-ethoxy-18/3-ethylestra-3,5-diene-17-one. The crystals are recrystallized from ether to give 30 g of the compound melting at 114°C to 115°C. 

To a solution of 3.0 g of the enol-ether compound obtained above in 50 ml of methanol, is added 1.5 g of sodium borohydride. After standing for 1 S hours at room temperature, the reaction solution is poured into 300 ml of water. The resulting precipitates are collected by filtration and recrystallized from ether to give 2.8 g of 3-ethoxy-18/3-ethylestra-3,5-dien-17/3-01 melting at 131°C to 133°C. 

A phenyl substituent at the y-carbon atom is a much weaker electron donor in comparison with the discussed above ethoxy and morpholin-4-yl groups. Nevertheless, l-(y-phenylallyl)benzotriazole 484 is still lithiated exclusively at the carbon a as it is evident from its reaction with aldehydes and ketones leading to dienes 486, resulting from... 

The reactions of 4-nitrobenzodifuroxan 242 with a series of common dienes, such as cyclopentadiene, cyclohexa-diene, isoprene, 2,3-dimethylbutadiene, and 1-acetoxybutadiene, with ethoxymethyleneacetylacetone were found to proceed very readily to afford stable cycloadducts, which are the result of highly stereoselective normal electron-demand (NED) Diels-Alder reactions. Due to the additional activation provided by the two adjacent furoxan rings, the nitroalkene double bond of compound 242 is also prone to undergo NED reactions with less reactive dienic structures, such as the enol form of ethoxymethyleneacetylacetone and the in situ generated 2-ethoxy-4-(2-furfur-yl)buta-l,3-diene <2004TL1037, 2005T8167>. 

Palladium-catalyzed cross-coupling of 19 with allyl bromide occurs exclusively at the vinylstannane moiety to give 1-ethoxy-1-silyl-1,4-diene 20. The following ether exchange with allyl alcohol causes the Glaisen rearrangement to give an acylsilane derivative 21 (Scheme 64).2... 

The presence of electron-donating substituents in the diene enables it to react with simple aldehydes thus both acetaldehyde and benzaldehyde add to 1-methoxy-1,3-butadiene at 50-65 °C under high pressure (20 Kbar) to give dihydropyrans as 70 30 mixtures of cis- and frans-isomers (equation 5)4. The combination of electron-rich diene/electron-poor dienophile makes it possible to perform the reaction under milder conditions. 2-Alkyl-l-ethoxy-1,3-butadienes and diethyl mesoxalate afford dihydropyrans almost quantitatively (equation 6)5. 

Beccalli et al. reported a synthesis of carbazomycin B (261) by a Diels-Alder cycloaddition using the 3-vinylindole 831 as diene, analogous to Pindur s synthesis of 4-deoxycarbazomycin B (619). The required 3-vinylindole, (Z)-ethyl 3-[(l-ethoxy-carbonyloxy-2-methoxy)ethenyl]-2-(ethoxy-carbonyloxy)indole-l-carboxylate (831), was synthesized starting from indol-2(3H)one (830) (620). The Diels-Alder reaction of the diene 831 with dimethyl acetylene dicarboxylate (DMAD) (535) gave the tetrasubstituted carbazole 832. Compound 832 was transformed to the acid 833 by alkaline hydrolysis. Finally, reduction of 833 with Red-Al afforded carbazomycin B (261) (621) (Scheme 5.99). 

Valence tautomerization to the bicyclic azetine (47 R1 = OEt, R2 = Me) has been observed in the photosensitized (PlfcCO or PhCOMe) ring contraction of the otherwise photostable 2-ethoxy-4,5-dihydro-3.H-azepine (46 R4 = OEt, R2 = Me) (71JOC1934). In contrast, sensitized photolysis of the dimethylamino derivative (46 R1 = NMe2, R2 = H) gave only polymers. Unsensitized photolysis in pyrex yields several cyclic products, all of which are attributable to the intermediacy of an unstable 7-azabicyclo[3.2.0]hepta-3,6-diene (47 R1 = NMe2, R2 = H) (73CC327). 

Butadienes substituted with alkoxy groups in the 2-position, e.g., 2-ethoxy-1,3-butadiene,6 have been prepared from methyl vinyl ketone, but they required several conversions and a tedious spinning-band distillation to purify the product. This slight modification of the House procedure has been used to conveniently prepare 2-trimethylsilyloxy-l,3-butadiene from the readily available methyl vinyl ketone. This one-step procedure has provided large amounts of a new and reactive diene for Diels-Alder reactions, as illustrated in Table I. 

The cyclocondensation of Danishefsky s diene 35 with alaninals of type 25, contrary to diene 32, requires neither elevated pressure nor high temperature. The zinc bromide-mediated reaction of 35 with alaninal 25 was followed by acidic workup, resulting in removal of both the trimethylsilyl protection and the ethoxy group [45,46] (Scheme 13). 

J. Jnrczalc, A. Gotfbiowski, and J. Raczko, Influence of the N-protecting group on the stereochemical course of [4+2]cycloaddition of l-ethoxy-3-[(trimethylsilyl)oxy] buta-l,3-diene to... 

Cycloaddition of 2-ethoxy-2,3-dihydro-4//-1,3-benzoxazin-4-one with conjugated diene 167 gave tetrahydropyrido[2,l-b][l,3]oxazin-6-ones (168) (71JHC865). Diels-Alder reactions of 3,4-dihydroisoquinolines and thioketenes (169), formed in situ, yielded 4,6,7,116-tetrahydro[l,3]ox-azino[2,3-a]isoquinoline-4-thiones [83AG(E)55 88CB1165],... 

Butene 4-Cyclohexyl-2-ethoxy-1.1,1-trifluoro- ElOb, 459 (F3C-COOR + -CH2-R) 2,4-Dodecadiene 12-Hydroxy-l,l,l-trifluoro- E10b2, 176f. (2-In —> 2,4-Dien)... 

Cycloaddition vs conjugative Michael-type addition of 2-ethoxy-3-morpholinobuta-1,3-diene (137) to nitroalkenes (136) has been thoroughly investigated. With 1-nitrocyclopentene (136a), carbocyclic products (138) largely predominated, whereas... 

Dihydropyran-4-ones can be prepared by addition of various nucleophiles to 3-ethoxy-5,6-dihydropyran-2-ones prepared from the hDA reaction between Brassard s diene and aldehydes <20050L2421>. 

The unsubstituted benzo-TA 263 that was generated in situ from 2-ethoxy-2,3-dihydrobenzo-TA 262 reacts with 1,3-dienes to give the Diels-Alder adducts 264 and 265 (73JHC149) possessing a cis-configuration according to the Woodward-Hoffmann rules for [2 + 4]-cycloaddition (Scheme 103). 

Although some carbenes are reported not to add to cyclopropenes207, there are several examples of inter- and intra-molecular addition leading initially to the formation of bicyclobutanes. l,2-Diphenylcyclopropene-3-carboxylates are converted to a mixture of three stereoisomeric bicyclo[1.1.0]butanes by reaction with ethoxy-carbonylcarbene generated from the thermolysis of ethyl diazoacetate an additional product is the diene (278) which is apparently formed by rearrangement of an intermediate zwitter ion208). It should be noted, however, that cyclopropenes readily undergo addition to diazo-compounds, and that subsequent transformations may then lead to bicyclobutanes (see Section 8), and that a free carbene may therefore not be involved in the above process. 

CN (11 J)-17- (ethoxy carbony Doxy]-11 -hydroxy-21 -(1 -oxopropoxy)pregna-1,4-diene-3,20-dione... 

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