Propadiene acidity

Addition of arylhydroxylamines to electrophilic allenes such as methyl propadienoate or l-methancsulfonyl-l,2-propadiene is another route to 0-vinyl derivatives[2]. The addition step is carried out by forming the salt of the hydroxylamine using NaH and the addition is catalysed with LiO CCFj. The intermediate adducts are cyclized by warming in formic acid. Yields are typically 80% or better. 

Tricarbon dioxide, C3O2, often called carbon suboxide and ponderously referred to in Chemical Abstracts as l,2-propadiene-l,3-dione, is a foul-smelling gas obtained by dehydrating malonic acid, CH2(C02H)2, at... 

The silicon- and sulfur-substituted 9-allyl-9-borabicyclo[3.3.1]nonane 2 is similarly prepared via the hydroboration of l-phenylthio-l-trimethylsilyl-l,2-propadiene with 9-borabicy-clo[3.3.1]nonane36. The stereochemistry indicated for the allylborane is most likely the result of thermodynamic control, since this reagent should be unstable with respect to reversible 1,3-borotropic shifts. Products of the reactions of 2 and aldehydes are easily converted inlo 2-phenylthio-l,3-butadienes via acid- or base-catalyzed Peterson eliminations. 

ETHYLENE GLYCOL ETHYL MERCAPTAN DIMETHYL SULPHIDE ETHYL AMINE DIMETHYL AMIDE MONOETHANOLAMINE ETHYLENEDIAMINE ACRYLONITRILE PROPADIENE METHYL ACETYLENE ACROLEIN ACRYLIC ACID VINYL FORMATE ALLYL CHLORIDE 1 2 3-TRICHLOROPROPANE PROPIONITRILE CYCLOPROPANE PROPYLENE 1 2-DICHLOROPROPANE ACETONE ALLYL ALCOHOL PROPIONALDEHYDE PROPYLENE OXIDE VINYL METHYL ETHER PROPIONIC ACID ETHYL FORMATE METHYL ACETATE PROPYL CHLORIDE ISOPROPYL CHLORIDE PROPANE... 

In contrast to the limited success with vinyl sulfides as components of [2 + 2] cycloadditions, allenyl sulfides show wide applicability. As illustrated in Scheme 8.91, Lewis acid-catalyzed [2 + 2] cycloadditions of l-trimethylsilyl-l-methylthio-1,2-propadiene (333) with a variety of electron-deficient olefins 336 provide cycloadducts 337 with excellent regioselectivity but with moderate stereoselectivity [175c], Nara-saka and co-workers reported the first Lewis acid-catalyzed asymmetric [2 + 2] cycloaddition of C-l-substituted allenyl sulfides 319 with a,/3-unsaturated compounds 338 using a chiral TADDOL-titanium catalyst. The corresponding cycloadducts 339 were obtained with 88-98% ee, but a low level of trans/cis selectivity (Scheme 8.92) [169,175d[. 

Potassium hexacyanoferrate(III), Hydrochloric acid, 4242 f Propadiene, 1124 Propadienedithione, 1350 f Propyne, 1125... 

Alcohols will add to allenes in the presence of trace amounts of acids to give vinyl ethers (or acetals) or allylic ethers.401 Analogous to the hydration of allenes, protonation occurs on the terminal carbon of the allenic functionality in 1,2-propadiene, 3-alky 1-1,2-propadienes and 1,3-dialkyl- 1,2-propadienes (equation 248).402 Addition of an alcohol to the resulting vinylic cation produces a vinylic ether, which may on further reaction form an acetal of the corresponding ketone. 

Aconitic acid, see -Propene-1,2,3-tricarboxylic acid, 2335 f Allene, see Propadiene, 1121... 

B. 2,3-Dibromo-1-(phenylsulfonyl)-1-propene. To a solution containing 25.4 g (0.14 mol) of 1-(phenylsulfonyl)-1,2-propadiene in 100 mL of acetic acid in a 250-mL, round-bottomed flask fitted with a dropping funnel is added 8.0 mL (0.14 mol) of bromine over a period of 30 min. The solution is stirred at room temperature for 8 hr, poured into 200 mL of water, and extracted with dichloromethane (3 x 100 mL). The dichloromethane layer is washed with 50 mL of a 1.0 M aqueous sodium ihiosulfate... 

Carbon suboxide, C3O2, 0=C=C=C=0 , also called l,2-propadiene-l,3-dione, is an evil-smelling unstable gas, bp +6.8 °C, which is obtained by the dehydration of malonic acid with P4O10 in vacuum at 140-150 °C (equation 6). Carbon suboxide polymerizes readily at room temperature to a yellow solid, and above 100 °C to a ruby-red water-soluble solid. Photolysis of C3O2 gives C2O ( C=C=0 ) as a reactive intermediate, which reacts with alkenes by carbon atom insertion (equation 7). 

The most common mode of reactivity of Y—H with unsaturated hydrocarbons in the absence of acidic hydrogens is 1,2-addition as shown in Scheme 5. The hydrides react with alkenes to form alkyl complexes, with 1,2-propadiene to form allyl systems, and with alkynes to form cis-alkenyl complexes (45). Crystallographic confirmation of the 1,2-addition mode of Y—H with unsaturated hydrocarbons was obtained using terf-butylnitrile as a substrate. The structure of the alkylideneamido product, [(C5Hs)2Y(/Li-N==CHCMe3)]2, was determined by X-ray crystallography. 

Introduction of an alkylthio group on the allene system increased the reactivity of the allene moiety in [2 + 2] cycloaddition reactions. It proved possible to conduct reactions of this allene at much lower temperatures. By adding Lewis acids, the reaction temperature could be decreased even more, as was illustrated by the Lewis acid catalyzed [2-1-2] cycioadditions of l-trimethylsilyl-l-methylthio-l,2-propadiene with a variety of electron-poor alkenes, including cyclic and non-cyclic enones, acrylates, methyl fumarate and acrylonitrile. When a chiral diol 21 based titanium catalyst was employed, the [2-1-2] cycloaddition reactions of /-acryloyl-l,3-oxazolidin-2-ones 17a and 17b with allenyl sulfides 18 yielded methylenecyclobutanes 19 and 20 with high optical purities (equation The highest yields were obtained with electron-poor allenophile 17b. 

PROPADIENE (463-49-0) Extremely flammable gas. Violent reaction with oxidizers, fluorine. Incompatible with aluminum chloride, aluminum tetrahydroborate nitromethane, magnesium perchlorate, nitrosyl fluoride, ozone, peroxyformic acid. Forms explosive material with nitric oxide, copper(I) perchlorate. May accumulate static electrical charges, and cause ignition. 

The reaction conditions for the metallation of propadiene show that this compound is readily metallated. Introduction of alkyl substituents causes a marked decrease of the kinetic acidity of the allenic protons. This is reflected in the higher temperature in the lithiation of 1,1-dimethylallene. 

Some specific compounds might be mentioned. A method has been devised for the preparation of optically active (2-aminopropyl)phosphonic acid by a procedure involving initial addition of optically active 1-phenylethylamine to a dialkyl (l,2-propadiene)phosphonate. This produces a mixture of cis and trans (aminoalkene)phosphonates which is reduced and the product hydrolysed and debenzylated. ... 

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