Ethyl reaction with allyl bromide

Ethoxy-l,3,2-oxazaphospholidine 59 was prepared as a single diastereomer from (-)ephedrine (42) and ethyl dichlorophosphite 57. Its Arbusov reaction with allyl bromide gave the corresponding allyl phosphonates 61a,b as a diastereomeric mixture which could be separated by flash column chromatography and crystallization (Scheme 21) [48], On applying a similar protocol, starting from... 

In contrast to ethyl diazoacetate, diethyl diazomalonate reacts with allyl bromide in the presence of Rh2(OAc)4 to give the ylide-derived diester favored by far over the cyclopropane (at 60 °C 93 7 ratio). This finding bespeaks the greater electrophilic selectivity of the carbenoid derived from ethyl diazomalonate. For reasons unknown, this property is not expressed, however, in the reaction with allyl chloride, as the carbenoids from both ethyl diazoacetate and diethyl diazomalonate exhibit a similarly high preference for cyclopropanation. 

Carbohydrate lactones have been used as the carbonyl reagent in the Reformatsky reaction. Thus, 2,3 5,6-di-O-cyclohexylidene-D-mannono-1,4-lactone [44, obtained by oxidation of the mannofuranose derivative (49)] reacted with ethyl bromoacetate and zinc to give the protected 2-deoxy-3-octulosonic acid ethyl ester (45a) in 69% yield (50). Ketonic hydrolysis with potassium hydroxide in aqueous methanol, followed by acidification and heating, afforded the 1-deoxyheptulose derivative 45b. Similarly, starting from compound 44, the 1-C-substituted allyl and propar-gyl lactols were prepared on reaction with allyl or propaigyl bromides in the presence of zinc (51). 

In addition, the use of enzyme selective inhibitors has turned out to be very effective. Reductions were performed by adding l,l,l-trifluoro-2,4-pentane-dione 1 to a yeast-water suspension with selected additives such as methylvinyl-ketone, allyl alcohol, alkanoic acids, ethyl chloroacetate or allyl bromide, all of them reported to affect the stereochemical course of baker s yeast reduction. In some cases, both the influence of the yeast/substrate ratio and the influence of the presence of glucose were considered. In the presence of alkanoic acids (acetic, fumaric, or oleic acid), no significant effect was observed. However, addition of methylvinyl-ketone, allyl alcohol, ethyl chloroacetate and allyl bromide to the reaction system affected the stereochemical course of the reduction of 1. In particular, (R)-(+)-2 was produced in the presence of ethyl chloroacetate and allyl bromide as additive. 

A total synthesis of ( )-aromatin has utilized the lithium anion of the dithiane of (E)-2-methyl-2-butenal as a functional equivalent of the thermodynamic enolate of methyl ethyl ketone in an aprotic Michael addition (Scheme 189) (81JOC825). Reaction of the lithium anion (805) with 2-methyl-2-cyclopentenone followed by alkylation of the ketone enolate as its copper salt with allyl bromide delivered (807). Ozonolysis afforded a tricarbonyl which cyclized with alkali to the aldol product (808). Additional steps utilizing conventional chemistry converted (808) into ( )-aromatin (809). 

The reaction of methyl ester of D-alanine 185 with 4-methoxy-2-nitrobenzenesulfonyl chloride 186 in presence of ethyl diisopropylamine gave the sulfonamide 187, which was alkylated with allyl bromide 188 to afford 189 (Scheme 41). Ozonolysis of 189 resulted in the formation of aldehyde 190, and the subsequent reductive cyclization with zinc and AcOH led to the benzothiadiazepine 120 through intramolecular reductive alkylation. Using similar reaction sequence, the 1,2,5-thiadiazepines 191 and 192 were also synthesized <2003JME1811>. 

The gas-phase elimination kinetics of ethyl oxamate, ethyl N,N-dimethyloxamate and ethyl oxanilate have been determined in a static reactor system, seasoned with allyl bromide and in the presence of a free radical inhibitor.12 These reactions are homogeneous, unimolecular and appear to proceed through moderately polar cyclic transition states. 

Nitromethane anion gives the corresponding N-allyl-3-(2-nitro-ethyl)- 2,3-dihydro-1-H-indole in 60% yield after photostimulated reaction with the bromide analogue, and in the presence of the enolate ion and acetone as an entrainment reagent (Scheme 10.51) [67]. 

A new approach to the abe ring system of the pentacyclic C20 diterpenoid alkaloids has been reported by van der Baan and Bickelhaupt.51 For the model system of major interest, (134) was prepared from (133) by reaction with cyano-acetamide. Treatment of (134) with allyl bromide gave almost exclusively C-alkylation, to afford (135). On heating (135) at 100—110°C, a Cope-type rearrangement to (136) was effected. This compound was then N-alkylated with ethyl iodide-DMF, the product being (137). Treatment of (137) with IV-bromosucc-... 

Alkylation reactions involving other electrophiles are known. For instance, treatment of the anion of nickel(II) corrole 2.105 with allyl bromide was found to afford a mixture of two compounds that proved to be C-allyl metallocorroles. The major product was found to be the 3-allyl-3-methyl-nickel(II) corrole 2.218, and the minor component the meso-d d y derivative 2.219 (Scheme 2.1.74). In the first instance, the regioselectivity of the addition (i.e., at the 3-position) was specifically confirmed by treating the 3,17-diethylcorrole 2.217 with allyl bromide this, as expected, afforded the 3-allyl-3-ethyl derivative 2.220. 

Compared with results obtained for ethyl diazoacetate, reactions of diazomethane with allyl bromide produce a dramatic reversal in the relative reactivities of the carbenoid species towards the nucleophilic bromide and the carbon-carbon double bond. These results are in accord with a greater electrophilic selectivity of the dialkoxycarbonyl carbenoid intermediate relative to the ethoxycarbonyl carbenoid. That increasing the electrophilicity of the carbenoid intermediate can reverse its reactivity towards the nucleophilic heteroatom relative to the olefin is consistent with the nature of this... 

The importance of the nucleophilicity of the heteroatom for product partitioning is shown for the interaction of ethyl diazoacetate with allyl halides, e.g. formation of 29 and 30. In contrast to the result for this diazo compound, rhodium-catalyzed reaction of diethyl di-azomalonate with allyl bromide yields practically no cyclopropane [Rh2(OAc)4 diethyl al-lyl(bromo)malonate (86%) and diethyl 2-bromomethylcyclopropane-l,l-dicarboxylate (6%) RhjCCO) 72 and 10%].2 ... 

This zinc-promoted reaction has been used with a variety of carbonyl compounds. Thus, the Luche conditions were applied in a synthesis of (-1-)-muscarine using an aldehyde derived from ethyl lactate [109]. Allyl halide condensation onto a-ketoamides of proline benzyl ester gave good diastereoselec-tivity when performed in the presence of zinc dust and pyridinium p-toluene-sulfonate in a water/THF mixture. In this way, a-hydroxy ketones were obtained with good enantioselectivity after removal of the chiral auxiliary [110]. Reactions of allyl bromide under the Luche conditions with y-aldo esters afforded y-hydroxy esters, which were converted in a one-pot reaction to y-allyl-y-butyro-lactones (Scheme 22) [111]. 

Reaction of the ethyl thiolactam 501 with allyl bromide gave the salt 502 which on base-catalyzed rearrangement afforded 503 and a mixture of isomers. Hydroboration and alkaline oxidation of each isomer gave a mixture of alcohols (504 and 505) which were converted to quebrachamine (82) in the standard manner (Scheme 26). 

With Trimethylchlorosilane. Rather recently [60] it was found that activation of zinc with TMClSi augmented the yield of Zn-Barbier reactions with allylic halides considerably. This unexpected activation by the silane was found earlier for Reformatsky reactions with ethyl 2-bromopropanoate [61] also trimethylchlorosilane-activated lead was applied in Pb-Barbier reactions with crotyl bromide [62] and allyl bromide [63]. 

Obtained by reaction of allyl bromide with 2,2, 4-trihydroxy-3-propylbenzophenone in the presence of potassium carbonate and potassium iodide in refluxing methyl ethyl ketone for 3 h (30%) [1029]. 

Preparation by reaction of allyl bromide on quinaceto-phenone with potassium carbonate in refluxing acetone (86%) [2226,2357], (73%) [3187] or in refluxing methyl ethyl ketone (52%) [3181]. 

Quaternization of dimethyldodecylamine with allyl bromide for the synthesis of the monomer was performed in ethyl acetate, in which the reaction proceeds relatively fast and in addition the quaternary salt precipitates readily. 

Chemical Properties.—Thietan is a useful starting material in the synthesis of macrocyclic compounds the first step in the sequence is the reaction of thietan with allyl bromide to give an 85% yield of allyl 3-bromopropyl sulphide. When cis- and tra j-3-ethyl-2-propylthietan were irradiated in the presence of mercury vapour they gave but-l-ene and cis- and tm 5-hept-3-ene. At low F. Sannicolo, Ann. Chim. (Italy), 1973, 63, 825. 

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