Ethyl allene

Phosphine-catalysed addition of ethyl allene carboxylate to aldehydes also involves the construction of the 5,6-bond. ... 

If, however, one compares the C chemical shifts 5cy of the methyl-ethyl-allenes 7 and 8 (Table 16), their corresponding C-chemical shifts are distinctly different. 

As a last example related to the preceding problem of relationships between scalar molecular properties of constitutional isomers, one observes that also in case of the molar refractions Rp of the methyl-ethyl-allenes 7 and 8 a nonadditivity holds (20). 

Methyl-penta-l,2-diene 1 -methyl-1 -ethyl-allene) (7) Total electron density 343, 368,... 

The alkylations proceeded much more slowly, when ethyl- or butyllithium in diethyl ether, prepared from the alkyl bromides, had been used for the metallation of allene, in spite of the presence of THF and HMPT as co-solvents. 

Carbonylation of the complex 548 proceeds in ethanol gives ethyl 3-chloro-3-butenoate (554), The lactone 555 and the two esters 556 and 557 are obtained by carbonylation of the dimeric complex 549. The oxidative carbonylation of allene in ethanol with PdCl2 gives ethyl itacoante (558), although the yield is low[498]. 

Didodecyldimetbylammonium bromide [3282-73-3] M 463.6, m 157-162 . Recrystd from acetone, acetone/ether mixture, then from ethyl acetate, washed with ether and dried in a vacuum oven at 60° [Chen et al. J Phys Chem 88 1631 1984 Rupert et al. J Am Chem Soc 107 2628 1985 Halpern et al. J Am Chem Soc 108 3920 1986- Allen et al. J Phys Chem 91 2320 1987]. 

Ethyl carhazate (A-ethoxycarhonyl hydrazine) [4114-31-2] M 104.1, m 44-48 , 51-52 , h 95.5 /10m, 92-95 /12mm, 100-102 /llmm. Fractionated using a Vigreux column until the distillate crystallises [Allen and Bell Org Synth Coll Vol III 404 1955.]... 

Ethyl chrysanthemate (ethyl 2,2-dimethyl-3 c and t -[2-methylpropenyl]-cyclopropane carboxylate) [97-41-6] M 196.3, b 98-102 /llmm, 117-121 /20mm. Purified by vacuum distn. The free trans-acid has m 54° (from, EtOAc) and the free cis-acid has m 113-116° (from EtOAc). The 4-nitrophenyl ester has m 44-45° (from pet ether) [Campbell and Harper J Chem Soc 283 1945 IR Allen et al. JOrg Chem 21 29 1957]. 

Ethyl chlorodifluoroacetate has been used in a silicon-induced Reformatsky-Claisen reaction of allyl chlorodifluoroacetates in the presence ot zinc as a route to 2,2-difluoro unsaturated acids [( S] (equahon 58) When this methodology is applied to chlorodifluoropropargylic esters, the corresponding allenic esters are formed [SS]... 

In most cases diazonium salts are not isolated, but are converted into products by reactions that can be carried out in situ. Moreover, it is actually recommended not to isolate these salts, not even for purification purposes, as many of them have a tendency to explode. In addition, the high solubility of most diazonium salts in water makes precipitation from this medium difficult. Therefore, to obtain solid diazonium salts the recommended method for many decades was to carry out diazotizations in ethanol followed by precipitation with ether. As inorganic salts of nitrous acid are scarely soluble in ethanol, Knoevenagel recommended alkyl nitrites (ethyl or isopentyl nitrite) as diazotization reagents as long ago as 1890. Various other solvents have subsequently been used for diazotizations with alkyl nitrites (see Saunders and Allen, 1985, p. 23 ff.), but as a method for obtaining solid diazonium salts this has been superseded by the isolation of diazonium tetrafluoroborates and, to a lesser degree, of hexafluorophosphates. 

The conclusion of Brown et a/.346,347 viz. that the increased reactivity along a series of alkyl halides is due to the increased polarisation of the carbon-halogen bond has been challenged by Allen and Yats348, who found constant meta para isomer ratios for methylation, ethylation, and isopropylation of toluene, and since this ratio reflects the selectivity and hence reactivity of the electrophile they con-... 

Allene, l,3-di-ferf-butyl-l,3-dicyano- [2,3-Pentadienedimtnle, 2,4-bis(l,l-di-methylethyl) ], 55, 38 ALLYL ALCOHOL [2 Propen 1 ol], 55, 1 Amberhte IRA-400, 55, 5 Amine, diethyl- [Ethanamme, IV-ethyl-],... 

Some remarks concerning the scope of the cobalt chelate catalysts 207 seem appropriate. Terminal double bonds in conjugation with vinyl, aryl and alkoxy-carbonyl groups are cyclopropanated selectively. No such reaction occurs with alkyl-substituted and cyclic olefins, cyclic and sterically hindered acyclic 1,3-dienes, vinyl ethers, allenes and phenylacetylene95). The cyclopropanation of electron-poor alkenes such as acrylonitrile and ethyl acrylate (optical yield in the presence of 207a r 33%) with ethyl diazoacetate deserve notice, as these components usually... 

In the presence of triphenylphosphine as a catalyst, benzotriazole adds readily to activated allenes. Its reaction with ethyl 2,3-butadienoate produces a mixture of adducts 149 (54%) and 150 (20%). Both derivatives form exclusively as (Tyi-isomers <2006T3710>. In a reaction of benzotriazole with dibenzoylacetylene and... 

Being a diastereomer of 450 with respect to the configuration of the sulfur atom, 458 was liberated from the triflate 457 by ethyl diisopropylamine and trapped by furan (Scheme 6.93). The resulting [4+ 2]-cycloadduct 459 was isolated in 62% yield and is a diastereomer of 451 [155, 171b], Typical for virtually all furan adducts of six-membered cyclic allenes, 451 and 459 display the mdo-configuration with respect to the 7-oxanorbornene skeleton. 

Saalfrank, Hoffmann and co-workers performed a number of reactions with tetra-alkoxyallenes such as 196 (Scheme 8.47) [1, 41, 105, 114—116] and demonstrated that this class of donor-substituted allenes can serve as a 1,3-dianion equivalent of malonic acid. Treatment of 196 with cyclopropyldicarboxylic acid dichloride 197 produces 2,4-dioxo-3,4-dihydro-2H-pyran 198 through release of two molecules of ethyl chloride [115]. Similarily, the reaction of this allene 196 with oxalyl chloride gives 3-chloromalonic acid anhydride derivative 199. This intermediate is a reactive dieno-phile which accepts 2,3-dimethyl-l,3-butadiene in a subsequent [4+2] cycloaddition to afford cycloadduct 200 in good yield [116]. 

A tertiary homopropargylic alcohol could also be prepared by treatment of ethyl acetate with two equivalents of B-allenyl-9-BBN. However, the reaction proceeded slowly and was not general for other esters, which proved to be unreactive, as were tertiary amides and alkyl halides. However, homopropargylic amines could be prepared in high yield and with minimal allenic byproduct through allenylboration of imines with B-allenyl-9-BBN (Eq. 9.24). 

At temperatures between -33and 0°C, l-cyano-l,2-allenes 574 can react with primary or secondary amines to afford unconjugated enaminic nitriles 575, which can be converted to conjugated enamines 576 at 200 °C [264, 265], The corresponding reaction of ammonia is relatively slow and was conducted at 60-70 °C to afford 3-amino-4-ethyl-2-hexenenitrile 577 together with a small precentage of iminyl nitrile 578 [264, 265],... 

Cydoaddition reactions of electron-deficient allenes are also known. In the presence of A1C13, ethyl 2,3-butadienoate (32) reacts with alkenes to give cyclobutyl-ideneacetic esters at room temperature [28]. 

The reaction of ethyl azidoformate (93) with tetramethylallene yielded triazoline 94 and oxazoline 95 [88]. The triazoline 94 was formed by [3 + 2]-cycloaddition of azide 93 to the allene. The oxazoline 95 may result from [3 + 2]-cycloaddition of car-bethoxynitrene (96), which is formed from 93 by nitrogen evolution, to the allene or by the [2 +1] addition of the nitrene and subsequent rearrangement. 

SYNTHESIS OF 4-(2-BROMO-2-PROPENYL)-4-METHYL-v-BUTYRO-LACTONE BY THE REACTION OF ETHYL LEVULINATE WITH (2-BROMO-ALLYL)DIISOPROPOXYBORANE PREPARED BY HALOBORATION OF ALLENE... 

Martin and Martin 51) have reported similar small (AJ= -0.2 to -0.45 Hz) changes for VHH in a series of alkyl substituted vinyl bromides. The same authors si> have repeated a 1.5 Hz decrease with increasing solvent polarity for the negative geminal coupling constant in allenic ketones of the form RCOCH = C=CH2 where R is methyl or ethyl. Reaction field interactions are suggested. 

It was already noted that activated enynes bearing an acceptor substituent at the double bond react with organocuprates under 1,6-addition to provide functionalized allenes (see Section III.A)38. Interestingly, the preference of these reagents for triple bonds persists even when the distance between the acceptor group and the triple bond is increased by the introduction of further double bonds. For example, lithium dimethylcuprate attacked ethyl 8,8-dimethyl-2,4-nonadien-6-ynoate at the triple bond exclusively, and regioselective... 

Synthesis of 4-(2-Bromo-2-Propenyl)-4-Methyl-Y-Butyrolactone by the Reaction of Ethyl Levulinate with (2-Bromoailyl)diisopropoxyborane Prepared by Haloboration of Allene. 

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