Ethyl 4-bromocrotonate

Ethyl 2-bromocrotonate, CH3CH=C(Br)COOC2H5 (1). The reagent is prepared by bromination of ethyl crotonate followed by dehydrobromination with DBU. 

The analogous vinyloxirane-dihydrofuran rearrangement has also been developed. Hudliclq et al. reported the thermal deconposition of vinyloxiranes, which were prepared by low-temperature addition of the lithium dienolate of ethyl-2-bromocrotonate to aldehydes. Subsequent pyrolytic rearrangement afforded the corresponding 2,3-dihydroftirans in variable yields fScheme 11.261. ... 

The reaction of various thiophene carbonyl compounds with ethyl bromocrotonates was carried out smoothly in the presence of zinc in... 

The sulfone-stabilized anions 7 reacted in much the same way with ethyl bromocrotonate but more cleanly, giving the cyclopropane carboxylates 8 exclusively in high yields98. The only observed products were the truws-substituted cyclopropanes. 

DL-Threonic acid (10) seemed to be a promising source of DL-threose. Therefore, other routes to 10 were elaborated. By a procedure consisting of five steps" 2-propenal (acrolein) — vinylglycoloni-trile — ethyl vinylglycolate — ethyl 4-bromocrotonate — 3-hydroxy-crotonic acid — 10, DL-threonic acid was obtained in an overall yield of 4.1%. Another synthesis of 10 was achieved17 in six steps starting... 

Methyl n-amyl carbinol. 247, 254 Methyl n-amyl ketone, 482 Methylaniline (mono), pure, from commercial methylaniline, 562, 570 P-Methylanthraquinone, 728, 740 Methyl benzoate, 780, 781 p-Methyl benzyl alcohol, 811,812 Methyl benzyl ketone, 727, 735 Methyl y-bromocrotonate, 926, 927 2-Methyl-2-butene, 239 Methyl n-butyl carbinol, 247,255 Methyl n-butyl ether, 314 Methyl n-butyl ketone, 475, 481 4-Methylcarbostyril, 855 p-Methylcinnamic acid, 719 4-Methylcoumarin, 853, 854 Methyl crotonate, 926, 927 Methylethylacetic acid, 354, 358 Methylethylethynyl carbinol, 468 Methyl ethyl ketone, 335, 336 purification of, 172 Methyl n-hexyl ether, 314 Methyl n-hexyl ketone, 335, 336 Methyl n-hexyl ketoxime, 348 Methyl hydrogen adipate, 938 Methyl hydrogen sebacate, 938,939 4-Methyl-7-hydroxycoumarin, 834 Methyl iodide, 287 Methyl isopropyl carbinol, 247,255 Methyl 4-keto-octanoate, 936... 

Various 3-substituted l-cyano-2-methylthioindolizines (68) have been prepared by treating a-[bis(methylthio)methylene]-2-pyridine acetonitrile with a-haloketones and ethyl-y-bromocrotonate nitromethane gave the 3-nitroso compound.80... 

Methyl derivatives of 2-oxo-2//-pyrido[l,2-a]pyrimidines were prepared by Kato et al.19 and Potts et al.2 by using 2-bromocrotonic acid and ethyl tetrolate, respectively. 

Fig. 4. 27. anti-Selectivity of an E2 elimination of HBr as a reason for the exclusive formation of f-configured a-bromocrotonic acid ethyl ester, syn-selectivity of an E2 elimination of HBr as a reason for the preferential formation of a Z-configured a-bromocrotonic acid ethyl ester. 

Reformatsky reaction of A-bromocrotonate. The regioselectivity of the Refor-matsky reaction of ethyl 4-bromocrotonate with cyclopentanone (equation I) is markedly dependent on the solvent and catalyst, a-Addition is favored in ether, whereas y-addition... 

A [2 + 3] dihydrofuran aimulation methodology was recently developed based on this rearrangement. Divinyloxiranes (142) were generated by the stereospecific addition of the lithium dienolate of ethyl a-bromocrotonate to al hydes, and the subsequent pyrolysis to dihydrofurans (143 Scheme 30) occurred in excellent isolated yields (except for R = Bu", Pr ). ... 

Vinylic bromine can be replaced fairly easily without reduction of the double bond. This is a characteristic difference from hydrogenolysis of vinylic chlorine and especially fluorine. Catalytic hydrogenation of ethyl a-methyl-3-bromocrotonate resulted in replacement of bromine and formation of ethyl a-methylcrotonate (equation 15). In 14-bromocodeinone (9), replacement of bromine occurs with a double bond shift to give neopinone (10 equation 16).4... 

The tanshinones are diterpenoid furanoquinones which occur in the roots of Salvia miltiorrhiza. The syntheses of tanshinone II and cryptotanshinone were accomplished from 1,2,4-trimethoxybenzene. This was converted by a Friedel-Crafts acylation to 2,4,5-trimethoxybenzoylpropionic acid and thence to the tetralone (125). The tetralone was condensed with ethyl y-bromocrotonate and the product converted directly to a naphthylbutyric ester. Curiously, an aromatic methoxy-group was displaced in this reaction. Reaction of the ethyl ester with methyl magnesium iodide and cyclodehydration afforded the tetra-hydrodimethoxyphenanthrene (126). The furan ring was added via the derivative (127) which underwent cyclization and decarboxylation to afford (128). Hydrolysis and oxidation gave the tanshinone (129). 

It is clear that during nucleophilic reactions of allylic halides carrying one EWG various other reaction pathways can occur in addition to MIRC reactions, e.g. addition, substitution, rearrangement and eliminationFor example, reaction of ethyl 4-bromocrotonate (273) with sodium ethoxide in ethanol only affords minor amounts of the 2-ethoxycyclopropane carboxylate (274) in addition to the substitution (276) and the addition-substitution (275) product (equation 83). Nevertheless, a cyclopropane... 

Ethyl 4-bromocrotonate (273) reacts as a Michael acceptor with carbanions derived from 288 stabilized by a sulphur substituent (sulphone, sulphoxide, sulphide). The conjugated addition is followed by displacement of bromide affording various cyclopro-panecarboxylates (289) (equation Also the reaction of methyl 4-bromocrotonate... 

The iridoid sesquiterpene (-)-specionin, an antifeedant to the spruce budworm, was synthesized by T. Hudlicky et al. using the low-temperature vinylcyclopropane-cyclopentene rearrangement as the key step. The substituted cyclopentenone precursor was first exposed to the lithium dienolate derived from ethyl 4-(dimethyl-fert-butylsilyloxy)-2-bromocrotonate at -110 °C to afford silyloxyvinylcyclopropanes as a mixture of exo and endo isomers (with respect to the vinyl group). The mixture was not separated but immediately subjected to TMSI/HMDS, and the corresponding tricyclic ketones were obtained in good yield. Similar results were obtained when TBAF in THF was used instead of TMSI. 

The best results are obtained with the use of alkali metal hydrides (NaH, KH) in THF, DME, or DMF. The reaction works well in THF or DME with activated halides such as ethyl bromoac-etate, ten-butyl bromoacetate, - ethyl 2-bromobutyratc, ethyl T-broniobulyrale.- (iodom-ethyl)trimethylstannane, " (iodomethyl)trimethylsilane, benzoyl bromide,- benzyl bro-mide, - farnesyl bromide,- " alkyl 4-bromocrotonates, l-(bromomethyl)naphtalene,- andN-bromomethylphthalimide but gives poor results with primary alkyl halides.- Primary and secondary alkyl halides, bromides and iodides (Scheme 8.16), react satisfactorily in dMF or DMSO, although bulky electrophiles give poor results. In DMSO the expected product is frequently contaminated by the dialkylation product. ... 

This reaction is cnrrently nsed for the preparation of synthetically nsefnl phosphonate reagents employed in modi lied retinal stndies. Thns, dietliyl 3-alkoxycarbonyl-2-propenylphosphonates are prepared in 72-91 % yields by the reaction of metiiyT or ethyP28,729 4 bromocrotonates with triethyl phosphite at 150-160°C. Similarly, diethyl 3-(etiioxycarbonyl)-2-methyl-2-propenylphosphonate is prepared in 81% yield from triethyl phosphite and ethyl 3-methyl-4-chlorocrotonate by heating at 180-200°C7 The diethyl (E)- and (Z)-3-ethoxycarbonyl-3-flnoro-2-methyl-2-propenylphospho-nates are respectively obtained from triethyl phospliite and ( )- or (Z)-4-bromo-2-flnoro-3-methyl-2-bntenoates at 140°C%°... 

Use of the new base makes it possible to extend the reaction of organoboranes to ethyl 4-bromocrotonate and thus effect a four-carbon-atom homologation. As an example, the reaction of triethylborane with ethyl 4-bromocrotonate in the presence of one equivalent of the base affords ethyl 3-hexenoate (79% trans) ... 

A9(l 1 )-Estrone methyl ether, 84-85 Etard oxidation, 62 Ethanalation, 73 Ethanolamine, 146 Ether cleavage, 7 Ethoxyacetyl chloride, 137 N-Ethoxycarbonylazepine, 103 N-Ethoxycarbonyl-2-ethoxy-l,3-dihydroquin-oline(EEDQ), 137 Ethoxyketene, 137-138 Ethylamine, 186 Ethyl azidoformate, 138 Ethylbenzene, 328 Ethylbenzenes, 15 Ethyl bromide, 159 Ethyl bromoacetate, 26, 28, 236 Ethyl 4-bromocrotonate, 236 Ethyl bromocyanoacetate, 237 Ethyl chlorodiazoacetate, 222... 

In a study of the reaction of ethyl 4-bromocrotonate with a variety of conjugated enones, Hudlicky and coworkers- observed almost exclusive formation of 1,2-a-products at very short reaction times in... 

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