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290 results on '"Macchia, Franco"'

1. Regiochemical control of the ring opening of aziridines by means of chelating processes: synthesis and ring-opening reactions of cis- and trans-aziridines derived from 4-(benzyloxy)cyclohexane

Author

Crotti, Paolo, Favero, Lucilla, Gardelli, Cristina, Macchia, Franco, and Pineschi, Mauro

Subjects
Ring-opening polymerization -- Research, Organic compounds -- Synthesis, Stereochemistry -- Research, Chemical reactions -- Research, Biological sciences, Chemistry
Abstract

The regiochemical outcome of the ring openings of cis- and trans-aziridines bearing a polar remote functionality were found to be dependant on the opening reaction conditions, whether standard, metal-assisted or strongly acidic. Therefore, the addition process can be almost completely controlled by regioalternating process. These results were determined in a conformationally semirigid bicyclic system in which the polar funtionality (OBn) is in a homoallylic relationship to the aziridine ring.

Published
1995

2. Regiochemical control of the ring opening of 1,2-epoxides by means of chelating processes: 7. Synthesis and ring-opening reactions of cis- and trans-oxides derived from 2-(benzyloxy)-3,6-dihydro-2H-pyran

Author

Chini, Marco, Crotti, Paolo, Gardelli, Cristina, and Macchia, Franco

Subjects
Epoxy compounds -- Analysis, Chromatography -- Analysis, Ring-opening polymerization -- Analysis, Stereochemistry -- Analysis, Biological sciences, Chemistry
Abstract

Flash chromatography separates cis- and trans epoxides occurring due to epoxidation of 2-(benzyloxy)-3,6-dihydro-2H-pyran with m-chloroperoxybenzoic acid. Ring-opening reactions of these epoxides with various nucleophiles reveal that a change from non-chelating to chelating conditions influences the regioselectivity. GC and NMR analyses reveal the amounts of regioisomeric products.

Published
1994

3. Synthesis and reactions of some 2,3-epoxy-1-alkanol derivatives

Author

Chini, Marco, Crotti, Paolo, Flippin, Lee A., Gardelli, Cristina, Giovanni, Elena, Macchia, Franco, and Pineschi, Mauro

Subjects
Organic compounds -- Synthesis, Epoxy compounds -- Research, Scission (Chemistry) -- Research, Coordination compounds -- Research, Biological sciences, Chemistry
Abstract

The synthesis and nucleophilic reactions of 2, 3-epoxy-1-alkanols allow a regiochemical study on the effect of remote polar functionalities on epoxide ring opening. The study shows that metal (Li+, Mg2+, Zn2+) chelation provides better, sometimes complete, C-3 regioselectivity than nonchelating cleavage conditions. Under chelation conditions, trans-epoxides show higher C-3 selectivity than cis-epoxides. Contrary to previous findings, free hydroxyls are not needed for chelation-controlled regioselectivity.

Published
1993

4. Synthesis and reactions of the cis- and trans-oxides derived from 3-(benzyloxy methyl)cyclohexene

Author

Chini, Marco, Crotti, Paolo, Flippin, Lee A., Gardelli, Cristina, and Macchia, Franco

Subjects
Organic compounds -- Synthesis, Epoxy compounds -- Research, Alicyclic compounds -- Usage, Olefins -- Usage, Nucleophilic reactions -- Research, Biological sciences, Chemistry
Abstract

The synthesis of cis- and trans-3-(benzyloxymethyl)-1, 2-epoxycyclohexanes allows the study of their nucleophilic addition reactions. In the presence of a metallic salt catalyst, the cis-epoxide forms chelate intermediates which invite a nucleophilic attack on the C-1 oxirane carbon, resulting in ring cleavage. Its preference for chelation thus sterically directs the site of cleavage. The trans-epoxide, on the other hand, is prevented from undergoing chelation reactions due to its conformation. Its ring opening reactions are based on steric factors alone.

Published
1992

5. Synthesis and reactions of the cis- and trans-oxides of 4-((benzyloxy)methyl)cyclohexene, 3-cyclohexenemethanol, and methyl 3-cyclohexenecarboxylate

Author

Chini, Marco, Crotti, Paolo, Flippin, Lee A., Macchia, Franco, and Pineschi, Mauro

Subjects
Organic compounds -- Synthesis, Alicyclic compounds -- Research, Alcohols -- Research, Esters -- Research, Olefins -- Research, Scission (Chemistry) -- Research, Epoxy compounds -- Research, Biological sciences, Chemistry
Abstract

The synthesis of cis- and trans-epoxides of five 4-substituted cyclohexanes leads to a stereochemical study of their ring-opening reactions with various nucleophiles. The study shows that ring opening of the trans-epoxides is influenced by a mix of stereoelectronic and conformational factors. The cis-epoxides, on the other hand, are affected in varying degrees by chelation of a metal ion by the epoxide oxygen and that of the C-4 substitutent. The chelation effect depends on the reaction conditions and on the nature and concentration of the metal ion. The carboxylic acid derivative is also affected by hydrogen bonding.

Published
1992

10. Rapporti tra Cenopalpus wainsteini (Livsh. e Mitrof.) ed alterazioni morfo-fisiologiche di Pinus halepensis Mill. nei rimboschimenti delle Murge pugliesi di nord ovest

Author

Macchia, Franco, Nuzzaci, Giorgio, and Triggiani, Oreste

Abstract

RELATIONSHIPS BETWEEN Cenopalpus wainsteini (LIVSH. AND MITROF.) (Acarina: Tenuipalpidae) AND MORPHOPHYSIOLOGICAL ALTERATIONS OF Pinus balepensis IN REPLANTING WITH TREES THE APULIAN MURGE OF THE NORTH WEST In the present paper the presence of Cenopalpus wainsteini has been reported with its damages to the re-afforest of Pinus halepensis in the Apulian Murge of the N.W. (Gravina). The spread of the species in examining the re-afforest should be tied to the difficulty in vegetation of P. halepensis. The difficult exists due to an insufficient amount of the water supply in the ground when the temperature of plant growth is excellent. Nella presente nota viene riportata la presenza, con relativi danni, del Cenopalpus weinsteini (Acarina: Tenuipalpidae) nei rimboschimenti a Pinus halepensis nelle Murge di nord ovest (Gravina). La diffusione di questa specie nel rimboschimento in esame sarebbe legata alle particolari difficoltà vegetative del Pinus halepensis dovute al fatto che, quando la temperatura per la crescita dalla pianta è ottimale, le riserve idriche del suolo sono insufficienti., Entomologica, Vol 18 (1983)

Published
2016
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11. Regio- and stereoselective ring opening of enantiomerically enriched 2-aryl oxetanes and 2-aryl azetidines with aryl borates

Author

Bertolini, Ferruccio, Crotti, Stefano, Di Bussolo, Valeria, Macchia, Franco, and Pineschi, Mauro

Subjects
Catechin -- Chemical properties, Catechin -- Structure, Heterocyclic compounds -- Structure, Heterocyclic compounds -- Chemical properties, Organoboron compounds -- Structure, Organoboron compounds -- Chemical properties, Transition metals -- Chemical properties, Biological sciences, Chemistry
Abstract

The regioselective ring opening of 2-aryl-subsituted four-membered heterocyclic rings with phenols, including catechol, is achieved by using aryl borates in mild and neutral reaction conditions without the help of any transition metal catalysts. Intramolecular cyclization has allowed a new access to 2-aryl-1,5-benzodioxepins in an enantioenriched form when reactive functionalities are present in the [beta]-aryloxy alcohol.

Published
2008

12. Synthesis and cyclodehydration of hydroxyphenols: a new stereoselective approach to 3-aryl-2,3-dihydrobenzofurans

Author

Bertolini, Ferruccio, Crotti, Paolo, Di Bussolo, Valeria, Macchia, Franco, and Pineschi, Mauro

Subjects
Phenols -- Structure, Phenols -- Chemical properties, Ring formation (Chemistry) -- Analysis, Dibenzofurans -- Structure, Dibenzofurans -- Chemical properties, Biological sciences, Chemistry
Abstract

A new stereoselective synthesis approach to substituted 3-aryl-2,3-dihydrobenzofurans by intramolecular cyclization of hydroxyphenols is described.

Published
2007

13. Catalytic regiodivergent kinetic resolution of allylic epoxides: A new entry to allylic and homoallylic alcohols with high optical purity

Author

Pineschi, Mauro, Moro, Federica Del, Crotti, Paolo, Bussolo, Valeria Di, and Macchia, Franco

Subjects
Carbon -- Optical properties, Carbon -- Research, Allyl resins -- Research, Biological sciences, Chemistry
Abstract

A novel regiodivergent kinetic resolution of a series of allylic epoxides with alkylzinc reagents is described. The results demonstrate the potential of chiral copper-phosphoramidite catalysts-stereoregulated synthesis of cyclic and homoallylic alcohols with optical purities.

Published
2004

14. Regiochemical control of the ring opening of 1,2-epoxides by means of chelating processes. 6. Opening reactions of 3,4-epoxytetrahydropyran

Author

Macchia Franco, Chini Marco, Crotti Paolo, and Gardelli Cristina

Subjects
Nucleophilic addition, Chemistry, Metal ions in aqueous solution, Organic Chemistry, Epoxide, Regioselectivity, Ring (chemistry), Biochemistry, Combinatorial chemistry, chemistry.chemical_compound, Nucleophile, Drug Discovery, Organic chemistry, Chelation
Abstract

The regiochemical control of the ring opening of epoxides bearing polar remote functionalities, through chelation processes assisted by metal ions, was verified in the title compound (4). The use of metal assisted procedures in several ring opening reactions of 4 leads to a modification of the regiochemical outcome, and the attack of the nucleophile on the C-4 oxirane carbon is highly favored.

Published
1994
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