Franco D'Onofrio

Direct amino-phenylselenylation of enoates: An easy route to α-phenylseleno-β-amino esters and β-lactams

Abstract A “one-pot” procedure to obtain α-phenylseleno-β-amino esters from the corresponding enoates is described. The target compounds are useful synthetic tools and direct precursors of new α-phenylseleno-β-lactams, which can be easily transformed into their α-alkylidene analogues. A direct procedure to obtain α-phenylseleno-β-amino esters from the corresponding enoates is described. The target compounds are direct precursors of new α-phenylseleno-β-lactams. Download : Download full-size image

Studies on Reactivity of Pyridinium Chlorochromate — Iodine System: An Efficient Method for Converting Enol Silyl Ethers into α-Iodo Ketones

Abstract A new synthesis of α-iodo carbonyl derivatives is described. They are obtained, in very high yields, through an original and efficient procedure, by reaction of enol silyl ethers with I2-PCC system.

The binary reagent PhSeClZnCl2: a powerful chloro-phenylselenenylating agent of electrophilic olefins

Abstract The binary reagent PhSeClZnCl 2 was found to be powerful for the stereocontrolled conversion of highly electrophilic olefins, such as maleate and fumarate esters, into the corresponding chloro phenylseleno derivatives in very high yields. Other olefins, such as methyl acrylate and methyl vinyl ketone, react virtually instantaneously.

Photochemical behaviour of halogeno-thiophenes: synthesis of 5-arylthiophene-2-carboxylic esters

Abstract The arylation of 5-halogenothiophene-2-carbonitrile and methyl 5-halogenothiophene-2-carboxylate by a photochemical process was investigated. Whereas 5-bromothiophene-2-carbonitrile ( 3 ) is completely unreactive, the corresponding iodine derivative ( 4 ) furnishes the dehalogenation product. In contrast, methyl 5-iodothiophene-2-carboxylate ( 6 ) gives the corresponding aryl and heteroaryl derivatives in good yields on irradiation in the presence of various aromatic substrates (benzene, p -xylene, naphthalene, thiophene, 2-bromothiophene and 2-chlorothiophene). The different reactivities of compounds 3 , 4 and 6 can be explained on the basis of the proposed mechanism which involves the formation of an exciplex: compounds 3 and 4 do not give the arylation products probably because of their low intersystem crossing efficiency; the different behaviour of compounds 3 and 4 can be explained by considering the triplet energy of the molecules. An application of this conversion to the synthesis of a naturally occurring bithiophene isolated from Arctium lappa , 5′-(1-propynyl)-2,2′-bithiophene-5-carboxylic acid ( 13 ), is reported.

BENZOPHENONE SENSITIZED REARRANGEMENT OF FURYLIDENTETRALONES

Abstract Benzophenone sensitized rearrangement of furylidentetralones into dihydronaphthofuran derivatives was described. All the obtained compounds ( 6a , b , c , d , f ) showed a trans -double bond in α-position on the furan ring. Only using the methoxy derivative 5e the formation of a little amount of cis -isomer was observed. Furylidenacetone, furylidenacetophenone, and furylidenindanone did not show this reaction in agreement with the hypothesis that the observed intramolecular rearrangement is strictly related to the presence of tetralone moiety. An explanation of this behaviour on the basis of steric hindrance to conjugation in the starting materials was reported.

SELENIUM-DIRECTED CONJUGATE ADDITION OF AMINES TO DIMETHYL 2-PHENYLSELENO FUMARATE : REGIO AND DIASTEREOSELECTIVE SYNTHESIS OF 2-PHENYLSELENO-3-AMINO SUCCINATES

Abstract Dimethyl 2-phenylseleno fumarate 1 acts as a strong Michael acceptor of amines, providing the corresponding 2-phenylseleno-3-amino succinates 2a and 2b in very high yields with complete regio- and good diastereoselectivity.

Photo-oxidation of 2-furyl-alkyl-phosphonates: Synthesis of new cyclopentenone derivatives

Abstract The furan ring in the title compounds was opened with singlet oxygen in methanol. New phosphonate cyclopentenone derivatives were synthesized.

Synthesis and photochemical behaviour of 4-nitroimidazoles in the presence of oxygen

Abstract Synthesis and photochemical properties of 1-aryl-4-nitroimidazoles are described. These compounds are good sensitizers of superoxide ion. Only 1-phenyl-2-methyl-4-nitroimidazole is a photosensitizer of singlet oxygen.

Reactions of 2,5-dihydro-2,5-dimethoxy-furan with phenylselenenylchloride: Regio- and stereocontrolled generation of highly functionalized C4 building-blocks

Abstract An efficient protocol for stereo- and regiocontrolled synthesis of small polyfunctional molecules is presented. The stereospecific addition of PhSeCl to 2,5-dihydro-2,5-dimethoxy-furan 1 in solvents, such as methylene chloride and methanol, gives cyclic and linear acetals 2 and 3, depending on the solvent used. Emphasis is given to the regiocontrolled hydrolysis of acetal groups for the preparation of stereodefined and highly functionalized C4 synthons, such as 8, 9 and 13.

Photochemical synthesis of bithienyl derivatives

The application of a photochemical arylation of thienyl derivatives to the synthesis of bithienyl compounds is reported. The syntheses of 5-phenyl-2-propynylthiophene and 5-but-3-en-1-ynyl-2,2′bithienyl are described using as starting materials a phenylthienyl and a bithienyl derivative obtained by this method. Furthermore, the photochemical synthesis of halogenobithienyl ketones via the photochemical coupling of a halogenothiophene and 2-acetyl-5-iodothiophene is described. This methodology furnishes a new approach to the synthesis of natural bithienyls. All the synthesized compounds are singlet oxygen photosensitizers, and are, therefore, potentially bioactive compounds.