Reactions on polymers with amine groups. V. Addition of pyridine and imidazole groups with acetylenecarboxylic acids

Unsaturated macromolecular carboxybetaines were obtained by reaction of poly(4-vinylpyridine) and poly(N-vinylimidazole) with propiolic acid. A kinetic model was presented for 4-methylpyridine. It consists of three coupled reactions: neutralization, addition which involves two molecules of acid and leads to a cation–anion pair structure, where the cation results from the addition of the amine nitrogen to the triple bond of acid, and an equilibrium reaction between the ion-pair structure and the betaine structure. The addition rate was found to be higher for poly(4-vinylpyridine) than for poly(N-vinylimidazole); it was also higher in water than in a water–methanol mixture. The reaction with acetylenedicarboxylic acid was carried out on poly(N-vinylimidazole), but the transformed units showed the structure that results from propiolic acid. The betaine products from 4-methylpyridine did not polymerize by radical initiation. The polymeric products show characteristics of photocrosslinking polymers. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1615–1623, 1998     

Reactions on polymers with amine groups. I. Reactions of vinylpridine polymers and of their model compounds with unsaturated carboxylic acids

The reactions of vinylpyridine polymers with α,β-unsaturated carboxylic acids such as acrylic, methacrylic, crotonic, itaconic, cinnamic, fumaric, and maleic acids were studied. It was found that, when reacted with acrylic, itaconic and fumaric acids. poly(4-vinylpyridine) gave macromolecular betaine products while with maleic acid, betaine as well as the corresponding salt was obtained. Poly(2-vinylpyridine) reacted with the same acids as poly(4-vinylpyridine) gave only the salts. No significant changes were observed with the two polymers when reacted with methacrylic, crotonic, and cinnamic acids. To attempt to rationalize these observations with the two macromolecular tertiary amines, the reactions of 4-methyl and 2-methylpyridines with the same carboxylic acids were investigated. The ¹H-NMR methodology was generally applied to elucidate the chemical structure obtained. © 1995 John Wiley & Sons, Inc.     

1,4-Conjugate addition of allyltrimethylsilane to α,β-unsaturated ketones

α,β-Unsaturated ketones smoothly undergo conjugate addition with allyltrimethylsilane in the presence of a catalytic amount of elemental iodine under very mild and convenient conditions to afford the corresponding Michael adducts in high yields with high selectivity.     

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.     

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.     

Oxaphospholes and Bisphospholes from Phosphinophosphonates and α,β‐Unsaturated Ketones

The reaction of a {W(CO)₅}‐stabilized phosphinophosphonate 1 , (CO)₅WPH(Ph)? P(O)(OEt)₂, with ethynyl‐ ( 2 a – f ) and diethynylketones ( 7 – 11 , 18 , and 19 ) in the presence of lithium diisopropylamide (LDA) is examined. Lithiated 1 undergoes nucleophilic attack in the Michael position of the acetylenic ketones, as long as this position is not sterically encumbered by bulky (iPr)₃Si substituents. Reaction of all other monoacetylenic ketones with lithiated 1 results in the formation of 2,5‐dihydro‐1,2‐oxaphospholes 3 and 4 . When diacetylenic ketones are employed in the reaction, two very different product types can be isolated. If at least one (Me)₃Si or (Et)₃Si acetylene terminus is present, as in 7 , 8 , and 19 , an anionic oxaphosphole intermediate can react further with a second equivalent of ketone to give cumulene‐decorated oxaphospholes 14 , 15 , 24 , and 25 . Diacetylenic ketones 10 and 11 , with two aromatic acetylene substituents, react with lithitated 1 to form exclusively ethenyl‐bridged bisphospholes 16 and 17 . Mechanisms that rationalize the formation of all heterocycles are presented and are supported by DFT calculations. Computational studies suggest that thermodynamic, as well as kinetic, considerations dictate the observed reactivity. The calculated reaction pathways reveal a number of almost isoenergetic intermediates that follow after ring opening of the initially formed oxadiphosphetane. Bisphosphole formation through a carbene intermediate G is greatly favored in the presence of phenyl substituents, whereas the formation of cumulene‐decorated oxaphospholes is more exothermic for the trimethylsilyl‐containing substrates. The pathway to the latter compounds contains a 1,3‐shift of the group that stems from the acetylene terminus of the ketone substrates. For silyl substituents, the 1,3‐shift proceeds along a smooth potential energy surface through a transition state that is characterized by a pentacoordinated silicon center. In contrast, a high‐lying transition state TS(E′–F′)_R=Ph of 37 kcal mol^?1 is found when the substituent is a phenyl group, thus explaining the experimental observation that aryl‐terminated diethynylketones 10 and 11 exclusively form bisphospholes 16 and 17 .     

Palladium-catalyzed conjugate addition type reaction of 5-iodopyrimidines with α,β-unsaturated ketones

The reaction of various 5-iodopyrimidines with α,β-unsaturated ketones in the presence of palladium diacetate-triphenylphosphine complex in triethylamine are investigated. In the reaction of 2,4-dialkoxy(or alkylthio)-6-methyl-5-iodopyrimidine the addition of pyrimidine to the carbon? carbon double bond of α,β-unsaturated ketones occurs. In the case of other pyrimidines, according to the decrease of steric hindrance at the 5-position on the pyrimidine ring, the ratio of conjugate addition product was decreased and the usual olefinic substituted product was increased.     

Kinetic simulations for cyclization of α,ω‐telechelic polymers

In this work, we conducted kinetic simulations to examine the effects of various experimental conditions on cyclization during the feed of α,ω‐telechelic polymers into a reaction mixture. The simulations showed that the interplay between the feed rate and rate coefficients for cyclization and multiblock formation were the dominant and controlling parameters. The simulations were in good agreement with previously published results on cyclization of α,ω‐telechelic polystyrene with different molecular weights by the Cu‐catalyzed azide/alkyne cycloaddition (CuAAC) reaction. They also showed that high dilution was not a necessary condition for cyclization and that high percentages of monocyclic could be rapidly produced in solutions that are more concentrated. Previously reported work demonstrated that cyclic polystyrene could be prepared in less than 9 min at 25 °C using the CuAAC “click” reaction. These simulations allow for optimization and better experimental design, leading to the possibility of large scale production of cyclic polymers. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

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.     

Enantioselective Palladium‐Catalyzed Oxidative β,β‐Fluoroarylation of α,β‐Unsaturated Carbonyl Derivatives

The site‐selective palladium‐catalyzed three‐component coupling of deactivated alkenes, arylboronic acids, and N‐fluorobenzenesulfonimide is disclosed herein. The developed methodology establishes a general, modular, and step‐economical approach to the stereoselective β‐fluorination of α,β‐unsaturated systems.     

Diastereoselective SmI2-mediated cyclisation of δ-oxo-α,β-unsaturated esters to cyclopropanols

In the presence of samarium diiodide and a proton source, δ-oxo-γ,γ-disubstituted-α,β-unsaturated esters readily cyclise with complete diastereocontrol to give anti-cyclopropanol products.     

Reactions of β-heteroatom substituted α,β-unsaturated ketones with dimethylsulfonium methylide

β-Alkoxy- and β-alkylthio α,β-unsaturated ketones react with dimethylsulfonium methylide (DMSM) to give a furan, while β-anilino α,β-unsaturated ketones give the pyrrole. β,β-Bis(alkylthio) α,β-unsaturated ketones react with DMSM to afford the methylene inserted products, λ,λ-bis(alkylthio) β,λ-unsaturated ketones.     

Origin of the Enantioselectivity in Organocatalytic Michael Additions of β‐Ketoamides to α,β‐Unsaturated Carbonyls: A Combined Experimental,Spectroscopic and Theoretical Study

The organocatalytic enantioselective conjugate addition of secondary β‐ketoamides to α,β‐unsaturated carbonyl compounds is reported. Use of bifunctional Takemoto’s thiourea catalyst allows enantiocontrol of the reaction leading either to simple Michael adducts or spirocyclic aminals in up to 99 % ee. The origin of the enantioselectivity has been rationalised based on combined DFT calculations and kinetic analysis. This study provides a deeper understanding of the reaction mechanism, which involves a predominant role of the secondary amide proton, and clarifies the complex interactions occurring between substrates and the catalyst.     

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.     

The reaction of active and stabilized phosphonium ylides with α,β-unsaturated carbonyl compounds [1]

The active ketenylidene-(2a) or thioketenylidenetriphenylphosphoranes (2b) react with 2-benzylidene-1,3-indandione (1), 5-benzylidenebarbituric acid (11), and 4-benzylidene-1,2-diphenyl-3,5-pyrazolidinedione (16) to give the corresponding pyranones and thioxopyranones (3a,b, 12a,b) and (17a,b), respectively. On the other hand, compounds 1 and 11 can be converted by reaction with the stabilized alkylidenephosphoranes 4a–e into the phosphoranylidenes 6a–e and 13a–e. Moreover, the oxaphosphinins 8 or 14 and the oxazaphosphinins 10 or 15 were obtained when compounds 1 and 11 were allowed to react with the phosphorane 7 and the iminophosphorane 9, respectively. Some of these new organophosphorus compounds are found to have insecticidal and molluscicidal properties against cotton leafworm Spodoptera littoralis larvae and Biomphalaria alexandrina snails. © 1997 John Wiley, & Sons, Inc.