Reaction of singlet oxygen with α,β-unsaturated aldimines

The reaction of singlet oxygen with N-1-(2-alkenylidene)-t- butylamines ( and ) gives the unsaturated hemiperacetal derivatives ( and 4) of the hydroperoxy aldimines ( and ). Several α, β-unsaturated aldimines which are held in the s-trans conformation failed to react with singlet oxygen.     

β-lithiations of carboxamides. Synthesis of β-substituted-α,β-unsaturated amides

N-Methyl-2-methyl-3-(benzotriazol-l-yl)propanamide, on treatment with butyllithium forms a dianion which on treatment with alkyl and benzyl halides, aldehydes and ketones affords monosubstituted products; with ethyl p-toluate, a lactam is formed. The alkylated derivatives eliminate benzotriazole in the presence of base to afford trisubstituted α,β-unsaturated amides.     

Reaction of Cα,O-dilithiooximes with functionalized carbonyl compounds. Part 2 . Reaction with α-chloroketones and α,β-unsaturated aldehydes and ketones

The reaction of Cα,O-Dilithiooximes 2 and α-chloroketones afforded 5-(hydroxymethyl)-Δ²-soxazolines 4 . α,β-Unsaturated aldehydes and ketones reacted with 2 to give the corresponding acyclic 1,2-addition products 5 . The latter were cyclized with phosphorus pentoxide to 5-vinyl-Δ²-isoxazolines 6 .     

The high resolution mass spectra of α,β-unsaturated and α-chloromercuri-α,β-unsaturated steroidal ketones

The high resolution mass spectra (500 eV) of some α,β-unsaturated steroidal ketones have been studied and compared with the spectra of the corresponding α-chloromercuri ketones. In the latter, the carbon-mercury bond frequently remains intact at the expense of the fission of two carbon-carbon bonds. The abundance of mercury-containing ions allows the use of the mercury atom fingerprint in confirming ring B fragmentation of the steroid nucleus at C(6)–C(7) and C(9)–C(10) for 5α-androst-1-ene-3,17-dione, 1,4-androstadiene-3,17-dione and their 2-chloromercuri derivatives; and at C(7)–C(8) and C(9)–C(10) for 1,4,6-androstatriene-3,17-dione, 1,4,6-androstarien-17 β-ol-3-one and their 2-chloromercuri derivatives. 2-Chloromercuri-1,4,6-androstatriene-3,17-dione and 2-chloromercuri-1,4,6-androstatrien-17 β-ol-3-one also give an abundant ion as the result of ring C fragmentation at C(8)–C(14) and C(11)–C(12), the chloromercuri group being replaced by a hydrogen atom. This ring C cleavage gives the only recognizable distinctive fragmentation ion for 1,4,6-pregnatriene-3,20-dione and 2-chloromercuri-1,4,6-pregnatriene-3,20-dione. For most of the mercurated steroids, the low resolution mass spectra (70 eV) are reported. In these spectra, the fragmentation patterns are similar to those obtained using the higher ionization energy employed for the high resolution spectra.     

Synthesis of α,β-unsaturated oxathiolanes

The formation of α,β-unsaturated oxathiolanes 2 from α,β-unsaturated carbonyl derivatives was achieved selectively and in high yields using the heterogeneous catalyst APSG·HCl.     

Regioselective synthesis of 3-hydroxyisoxazoles and 5-isoxazolones from β-amino α,β-unsaturated esters

The regioselective synthesis of 3-hydroxyisoxazoles and 5-isoxazolones is accomplished by the reaction of β-amino α,β-unsaturated esters with hydroxylamine hydrochloride in the presence of appropriate bases. The total yield of isoxazole derivatives is sensitively influenced on the β-substituent group of the esters.     

Reactions of α,β-unsaturated ketones with cyanoacetamide

3-Aryl-1-phenyl-2-propen-1-ones Ia-f and aroylphenylacetylenes Va-d reacted under reflux for 3 hours with cyanoacetamide in the presence of sodium ethoxide to give the corresponding 4-aryl-3-cyano-6-phenyl-2-(1H)pyridones VI. However, when ketones Ia-e were refluxed with cyanoacetamide for one hour in the presence of sodium ethoxide or piperidine, they gave the corresponding 4-aryl-3-cyano-3,4-dihydro-6-phenyl-2-(1H)pyridones IIIa-e, which upon heating with selenium gave the corresponding 2-pyridones VI. The structures of the products are based on chemical and spectroscopic evidence.     

On the mechanism of isomerization in the esters of some α,β-unsaturated carboxylic acids—II

The effect of a phenyl group on the mechanisms of isomerization in the ionized methyl esters of simple α,β-unsaturated acids (methyl acrylate and related compounds) has been investigated with the aid of deuterium labelling as well as information from mass analysed ion kinetic energy spectra and first field free region metastable peak shapes. Substitution of a hydrogen atom of the O? CH₃ group by a phenyl group (benzyl acrylate and homologues) greatly enhances the rate of [ester] → [acid] isomerizations (loss of H₂O and COOH˙). It is inferred that this is due to an accelerating effect of the phenyl group on the first and the third steps (ring opening of the key intermediate ion which has the structure of the ionized enol form of γ-butyrolactone) of the reaction whose mechanism is basically the same as that in methyl acrylate. A phenyl group present at the α- or β-position of the vinylic double bond appears to suppress the [ester] → [acid] isomerization in some compounds by promoting other reactions or opening up a new reaction pathway, i.e. the loss of CH₂O from ionized methyl atropate for which mechanisms are proposed.     

Reaction of α,β-unsaturated carbodiimides with enamines leading to fused pyridine derivatives

The treatment of (5,5-dimethyl-3-oxo-1-cyclohexenyl)iminotriphenylphosphorane ( 2 ) with phenyl isocyanate ( 3a ) gave N-(5,5-dimethyl-3-oxo-1-cyclohexenyl)-N'-phenylcarbodiimide ( 4a ) in situ. The reaction of 4a with enamines proceeded smoothly to afford the pyridine ring formation with the elimination of amine. This means that 4a is regarded as a new class of 2-aza-1,3-butadiene. The scopes and limitation of this reaction are also discussed.     

Mass spectra of some acyclic α,β-unsaturated aldehydes,ketones and esters

The mass spectra of a series of aliphatic acyclic α,β-unsturated aldehydes, ketones and ester have been examined. The spectra do not show evidence for McLafferty rearrangements, alkoxyl migration or for fragmentations which are dependent upon the s-trans or s-cis conformations of the compounds. There is some evidence for cis-trans isomerism about the double bond.     

Condensation of 3-methylbenzoxazolinone with α,β-unsaturated acids

The reaction between 3-methylbenzoxazolinone and some unsaturated acids in PPA leads to mixtures of compounds, depending on the acid: 6-crotonyl- (or cinnamoyl)-3-methylbenzoxazolinones, 2,3-dihydro-2,5-(or 2,7)dioxo-3-methylcyclopenta[f]benzoxazoles and 6-(3-oxo-indanyl)-3-methylbenzoxazolinones. The structure of the products was established by ¹³C and ¹H nmr spectroscopy and (or) by independent synthesis. Possible mechanisms of the reaction are discussed; when competition is possible as in the last step of the cyclization, the benzene ring shows a higher reactivity than the aromatic nucleus of the benzoxazolinone; the contrary is observed when the benzene ring is p-chloro-substituted.     

Applications of 1,4-addition of grignard reagents to α,β-unsaturated acid derivatives. III—configuration studies of α,β-diaryl-α,β-dialkylpropionitriles

The configuration of twenty-four different α,β-diaryl-α,β-dialkylpropionitriles has been determined using nuclear magnetic resonance spectra. The erythro form showed greater deshielding of the methine hydrogen and alkyl groups in its spectra than the corresponding threo isomer. The former, however, showed less deshielding of the aryl groups than the threo isomer. Infrared spectra were not suitable for assignments of configuration.     

The reaction of α,β-unsaturated aldimines with benzofuroxan

Benzofuroxan reacts with imines derived from crotonaldehyde and cinnamaldehyde, to form 2-imino-methylquinoxaline 1,4-dioxides.     

Reaction of perfluoroalkanesulfonyl halide: 3. The reactions of perfluoroalkanesulfonyl bromide with α, β-unsaturated esters and chemical conversions of the products

The reactions of perfluoroalkanesulfonyl bromide with α, β-unsaturated esters were studied in detail. The reaction products were further converted to a series of perfluoroalkyl-substituted α, β-unsaturated acids or esters, α-amino acids and γ-lactones. A peculiar peak (M+15) was found to appear in the mass spectra of some perfluoroalkyl-substituted methyl esters. It was interpreted to be the result of a CH₃ group transfer to the molecular ion. Magnetic nonequivalence was observed in the ¹⁹F NMR spectra of CF₂ group linked to CH₂ in compounds 2f, g and 3f, g which showed a typical AB pattern, and was attributed to the effect of steric hindrance.     

Lipophilic Functionalized Cobyrinic-Acid Derivatives. Part 1. Cobester α-monoacids (α,α,α,β,β,β-hexamethyl α-hydrogen Coα, Coβ-dicyanocobyrinates)

The four α,α,α, β,β,β,-hexamethyl α-hydrogen Coα, Coβ-dicyanocobyrinates 2b, d–f , with a free b-, d-, e-, and f-propionic-acid function, respectively, were prepared by partial hydrolysis of heptamethyl Coα, Coβ-dicyanocobyrinate (cobester; 1 ) in aqueous sulfuric acid. The cobester monoacids 2b, d–f were obtained as a ca. 1:1:1:1 mixture which was separated. The monoacids were purified by chromatography and isolated in crystalline form. The position of the free propionic-acid function was determined by an extensive analysis of 2b, d–f using 2D-NMR techniques; an analysis of the C,H-coupling network topology resulted in an alternative assignment strategy for cobyrinic-acid derivatives, based on pattern recognition. Additional information on the structure of the most polar of the four hexamethyl cobyrinates, of the b-isomer 2b , was also obtained in the solid state from a single-crystal X-ray analysis. Earlier structural assignments based on 1D-NMR spectra of the corresponding regioisomeric monoamides 3b, d–f (obtained from crystalline samples of the monoacids 2b, d–f ) were confirmed by the present investigations.     

A novel synthesis of α,β-unsaturated phosphonates

A stereoselective synthesis of α,β-unsaturated phosphonates based on the reaction of S-(β-oxoalkyl)-dithiophosphates and Se-(β-oxoalkyl)selenophosphates with sodium dialkyl phosphites is described.