Roman Mazurkiewicz

Synthesis and rearrangement of 4-imino-4H-3,1-benzoxazines

SummaryN-Acylanthranilamides react with dibromotriphenylphosphorane in the presence of triethylamine as HBr captor to give 4-imino-4H-3,1-benzoxazines in good yields. If the reaction is carried out without acid acceptor, N-acetylanthranilamides yield 2-methyl-4-quinazolones, whereas N-benzoylanthranilamides give 2-phenyl-4-imino-4H-3,1-benzoxazines. It has also been found that 2-methyl-4-imino-4H-3,1-benzoxazines rearrange under the influence of HCl or HBr into the respective 2-methyl-4-quinazolones; 2-phenyl-4-imino-4H-3,1-benzoxazines, however, do not undergo such a rearrangement.ZusammenfassungDie Umsetzung von N-Acyl-anthranilsäure-amiden mit Triphenyldibromphosphoran in Gegenwart von Triethylamin als HBr-Akzeptor führt mit guten Ausbeuten zu 4-Imino-4H-3,1-benzoxazinen. Wird die Reaktion ohne säurebindendes Mittel durchgeführt, dann entstehen aus N-Acetyl-anthranilsäure-amiden 2-Methylchinazolone-4, jedoch erhält man aus N-Benzoylanthranilsäure-amiden 2-Phenyl-4-imino-4H-3,1-benzoxazine. 2-Methyl-4-imino-4H-3,1-benzoxazine erleiden unter dem Einfluß von HBr oder HCl eine Umlagerung in entsprechende 2-Methylchinazolone-4, während 2-Phenyl-4-imino-4H-3,1-benzoxazine zu einer solchen Umlagerung nicht befähigt sind.

α-Amidoalkylating Agents: Structure, Synthesis, Reactivity and Application

Abstract This review provides a summary of a wide range of α-amidoalkylating reagents and their precursors, especially novel developments in their synthesis and applications in a wide variety of inter- and intramolecular α-amidoalkylation reactions with O , N , S , P , C and other nucleophiles. A special attention is paid to (1) the introduction of new α-amidoalkylation reagents that join easy access from simple starting materials, structural diversity, high stability, easy handling and storage and high reactivity toward nucleophilic reagents under mild conditions; (2) the development of intramolecular α-amidoalkylation reactions to cyclic products via N -acyliminium ion or N -acylimine cyclizations; (3) the recent development of stereoselective α-amidoalkylation reactions using asymmetric catalysis, and (4) the application of α-amidoalkylation reactions for the synthesis of natural and/or bioactive compounds.This review provides a summary of a wide range of α-amidoalkylating reagents and their precursors, especially novel developments in their synthesis and applications in a wide variety of inter- and intramolecular α-amidoalkylation reactions with O, N, S, P, C and other nucleophiles. A special attention is paid to (1) the introduction of new α-amidoalkylation reagents that join easy access from simple starting materials, structural diversity, high stability, easy handling and storage and high reactivity toward nucleophilic reagents under mild conditions; (2) the development of intramolecular α-amidoalkylation reactions to cyclic products via N-acyliminium ion or N-acylimine cyclizations; (3) the recent development of stereoselective α-amidoalkylation reactions using asymmetric catalysis, and (4) the application of α-amidoalkylation reactions for the synthesis of natural and/or bioactive compounds.

Novel synthesis and rearrangement of 3,1,5-benzoxadiazepines

N,N′-Diacyl-o-phenylenediamines react with dibromotriphenylphosphorane in the presence of triethylamine as HBr captor to give 3,1,5-benzoxadiazepines in good yields. If the reaction is carried out without acid acceptor the initially formed 3,1,5-benzoxadiazepine finally rearranges into 1-acylbenzimidazole. It has also been found that the isolated 2,4-dimethyl-3,1,5-benzoxadiazepine rearranges under the influence of hydrogen bromide into 1-acetyl-2-methylbenzimidazole.ZusammenfassungDie Umsetzung von N,N′-Diacyl-o-phenylendiaminen mit Triphenyldibromphosphoran in Gegenwart von Triethylamin als HBr-bindendes Mittel führt mit guten Ausbeuten zu den 3,1,5-Benzoxadiazepinen. Wird die Reaktion ohne säurebindendes Mittel durchgeführt, dann erleidet das anfänglich entstandene 3,1,5-Benzoxadiazepin eine Umlagerung in 1-Acylbenzimidazol. Es wurde auch gefunden, daß das isolierte 2,4-Dimethyl-3,1,5-benzoxadiazepin unter dem Einfluß des Bromwasserstoffs in 1-Acetyl-2-methylbenzimidazol umgelagert wird.

α-Amidoalkylating Agents from N-Acyl-α-amino Acids: 1-(N-Acylamino)alkyltriphenylphosphonium Salts

N-Acyl-α-amino acids were efficiently transformed in a two-step procedure into 1-N-(acylamino)alkyltriphenylphosphonium salts, new powerful α-amidoalkylating agents. The effect of the α-amino acid structure, the base used [MeONa or a silica gel-supported piperidine (SiO(2)-Pip)], and the main electrolysis parameters (current density, charge consumption) on the yield and selectivity of the electrochemical decarboxylative α-methoxylation of N-acyl-α-amino acids (Hofer-Moest reaction) was investigated. For most proteinogenic and all studied unproteinogenic α-amino acids, very good results were obtained using a substoichiometric amount of SiO(2)-Pip as the base. Only in the cases of N-acylated cysteine, methionine, and tryptophan, attempts to carry out the Hofer-Moest reaction in the applied conditions failed, probably because of the susceptibility of these α-amino acids to an electrochemical oxidation on the side chain. The methoxy group of N-(1-methoxyalkyl)amides was effectively displaced with the triphenylphosphonium group by dissolving an equimolar amount of N-(1-methoxyalkyl)amide and triphenylphosphonium tetrafluoroborate in CH(2)Cl(2) at room temperature for 30 min, followed by the precipitation of 1-N-(acylamino)alkyltriphenylphosphonium salt with Et(2)O.

N-Acyl-a-triphenylphosphonioglycinates:A Novel Cationic Glycine Equivalent and its Reactions with Heteroatom Nucleophiles

Summary. Two simple and convenient methods of transforming easily accessible 4-phosphoranylidene-5(4H)-oxazolones into N-acyl-α-triphenylphosphonioglycinates are described. N-Acyl-α-triphenylphosphonioglycinates react smoothly with heteroatom nucleophiles in the presence of DBU or triethylamine yielding the corresponding α-functionalized glycine derivatives.Zusammenfassung. Zwei einfache Methoden zur Überführung der leicht zugänglichen 4-Phosphoranyliden-5(4H)-oxazolone in N-Acyl-α-triphenylphosphonionoglycinate werden beschrieben. Die N-Acyl-α-triphenylphosphonionoglycinate reagieren leicht mit Heteroatomnucleophilen in Gegenwart von DBU oder Triethylamin zu den entsprechenden α-funktionalisierten Glycinderivaten.

N-Acyl-α -triphenylphosphonio-α -amino Acids: Synthesis and Decarboxylation to α -(N-Acylamino)alkyltriphenylphosphonium Salts

4-Phosphoranylidene-5(4H)-oxazolones 1 undergo hydrolysis in THF in the presence of HBF 4 at room temperature to give N-acyl-α -triphenyphosphonioglycines 3 (R 2 = H) in very good yields. 4-Alkyl-4-triphenylphosphonio-5(4H)-oxazolones 2 react with water in CH 2 Cl 2 /THF solution without any acidic catalyst at 0–5°C in a few days yielding N-acyl-α -triphenylphosphonio-α -amino acids 3 (R 2 = Me) or α -(N-acylamino)alkyltriphenylphosphonium salts 4 (R 2 = alkyl, other then Me). α -Triphenylphosphonio-α -amino acids 3 upon heating to 105–115°C under reduced pressure (5 mm Hg) or upon treatment with a Hünig base in CH 2 Cl 2 at 20°C undergo decarboxylation to give the corresponding α -(N-acylamino)-alkyltriphenylphosphonium salts 4 , usually in very good yields.

Amidoalkylating Properties of 1-(N-Acylamino)Alkyltriphenylphosphonium Salts

Abstract Easily accessible 1-(N-acylamino)alkyltriphenylphosphonium salts react smoothly with nitrogen, sulfur, phosphorus and oxygen nucleophiles in the presence of (i-Pr)2EtN to give the expected α-amidoalkylation products, usually in good or very good yields. α-Amidoalkylation of dialkyl malonates or acetylacetates requires the application of a much stronger base (DBU) and gives the best results under the influence of microwave irradiation. α-Amidoalkylation of enamines was carried out successfully in the presence of (i-Pr)2EtN in a microwave reactor. 1-(N-Acylamino)alkyltriphenylphosphonium salts can be considered as new, convenient and effective α-amidoalkylation agents. GRAPHICAL ABSTRACT

Comparative Studies on the Amidoalkylating Properties of N-(1-Methoxyalkyl)Amides and 1-(N-Acylamino)Alkyltriphenylphosphonium Salts in the Michaelis–Arbuzov-Like Reaction: A New One-Pot Transformation of N-(1-Methoxyalkyl)Amides into Phosphonic or Phosphinic Analogs of N-Acyl-α-Amino Acids

Abstract It was demonstrated that N-(1-methoxyalkyl)amides do not react with trimethyl phosphite under neutral or basic conditions. The treatment of N-(1-methoxyalkyl)amides with trialkyl phosphites or dialkyl phosphonites, triphenylphosphonium tetrafluoroborate, and Hünigs base caused immediate formation of the corresponding 1-(N-acylamino)-alkyltriphenylphosphonium tetrafluoroborates, followed by the slow Michaelis–Arbuzov-like reaction of phosphonium salt with phosphites or phosphonites to α-(N-acylamino)-alkanephosphonic or α-(N-acylamino)alkanephosphinic acid esters, respectively. A plausible mechanism of the considered transformations, assuming an equilibrium between N-(1-alkoxyalkyl)amide, triphenylphosphonium tetrafluoroborate, 1-(N-acylamino)alkyltriphenyl-phosphonium salt, N-acylimine, and N-acyliminium salts, is discussed. GRAPHICAL ABSTRACT

A Novel Synthesis of 1-Aminoalkanephosphonic Acid Derivatives from 1-(N-Acylamino)- alkyltriphenylphosphonium Salts

Efficient and convenient procedures for the α-amidoalkylation of trialkylphosphites with 1-(N-acylamino)alkyltriphenylphosphonium salts followed by a Michaelis–Arbuzov-type reaction to afford 1-(N-acylamino)alkanephosphonic acid esters have been developed. High yields and simple isolation and purification protocols are the main advantages of this method.

Copper salt-crown ether systems as catalysts for the oxidation of isopropyl arenes with tertiary hydroperoxides to peroxides

Abstract Symmetrical and unsymmetrical peroxides can be obtained by the oxidation of isopropyl arenes with tertiary hydroperoxides in the presence of copper salt–crown ether as catalysts. The efficiency of the investigated catalytic system enhances markedly in the presence of some alkali metal salts, with a cation diameter corresponding to the inner diameter of the crown ether. The oxidation of isopropyl arenes with hydroperoxides in the presence of a copper salt–crown ether–alkali metal salt catalytic system proved to be a simple and efficient method for the synthesis of ditertiary peroxides. A possible mechanism of this phenomenon is discussed. The results obtained confirm strongly that phase transfer catalysis operates in the investigated reaction.