Franco Macchia

Metal salts as new catalysts for mild and efficient aminolysis of oxiranes

Abstract A new, simple, efficient, inexpensive, anti stereoselective, highly regioselective method for aminolysis of 1,2-epoxides, by means of metal salts, is described.

Lanthanide(III) trifluoromethanesulfonates as extraordinarily effective new catalysts for the aminolysis of 1,2-epoxides

Abstract Lanthanide(III) trifluoromethanesulfonates (triflates), such as Yb(OTf) 3 , Nd(OTf) 3 and Gd(OTf) 3 , catalyze in a extraordinarily efficient way the aminolysis of 1,2-epoxides, affording the corresponding β-amino alcohols, at room temperature and in a non-protic solvent (CH 2 Cl 2 or toluene), in very good yields. The reactions are completely anti stereoselective and highly regioselective.

Efficient metal salt catalyzed azidolysis of epoxides with sodium azide in acetonitrile

Abstract A new, simple, efficent, completely anti stereoselective method for the azidolysis of 1,2 epoxides with NaN3 in acetonitrile, by means of metal salts, is described. The use of a non-protiu solvent makes this method very competitive with the other methods previously reported.

Easy direct stereo- and regioselective formation of β-hydroxy nitriles by reaction of 1,2-epoxides with potassium cyanide in the presence of metal salts

Abstract A simple efficient, anti stereoselective, and highly regioselective method for the synthesis of β-hydroxy nitriles by the direct opening of 1,2-epoxides with KCN in acetonitrile, in the presence of metal salts, is described. This new method appears to be competitive with the other methods previously reported.

Regio- and Stereoselective Synthesis of β-Halohydrins from 1,2-Epoxides with Ammonium Halides in the Presence of Metal Salts

Abstract A simple efficient, stereoselective and regioselective method for the synthesis of β-chlorohydrins, β-bromohydrins, and β-iodohydrins by the direct opening of 1,2-epoxides with the corresponding ammonium halide in acetonitrile, in the presence of metal salts, is described. This new method appears to be of general use and competitive with the other methods previously reported.

Catalytic Enantioselective Carbon-Carbon Bond Formation by Addition of Dialkylzinc Reagents to Cyclic 1,3-Diene Monoepoxides.

Abstract Chiral copper complexes of 2,2′-binaphthyl-based phosphorus amidites are shown to be highly effective catalysts for the conjugate addition of dialkylzinc reagents to vinyloxiranes. The corresponding allylic alcohol reaction products (S N 2′-pathway) were obtained with moderate to high regioselectivity. Both direct- (S N 2-pathway) and conjugate-opening addition (S N 2′-pathway) seem to proceed with complete anti stereoselectivity. The enantioselectivity of these addition reactions according to a kinetic resolution protocol turned out to be high (>90% ee) with 1,3-cyclohexadiene and 1,3-cycloheptadiene monoepoxides.

Regio- and Stereoselective Ring Opening of Enantiomerically Enriched 2-Aryl Oxetanes and 2-Aryl Azetidines with Aryl Borates

The regioselective ring opening of 2-aryl-substituted four-membered heterocyclic rings with phenols, including catechol, was achieved by the use of aryl borates in mild and neutral reaction conditions without the aid of any transition metal catalysts. While N-alkyl azetidines were found not to be reactive, optically active N-tosyl azetidines gave the corresponding beta-aryloxy amines in a racemic form, thus indicating the considerable carbocationic character of the transition state. The introduction of a hydroxyl group in the azetidine ring (i.e., an azetidinol), able to anchor the aryl borate and to direct the subsequent nucleophilic delivery, was shown to determine the ring-opening process with predominant inversion of configuration. When enantiomerically enriched 2-aryl oxetanes were used, the reduced extent of racemization observed (up to 93:7 er) was rationalized by an intramolecular delivery through a six-membered transition state, giving beta-aryloxy alcohols with a predominant retention of configuration (i.e., a syn-stereoselective ring opening). The aryloxy alcohols obtained, endowed with suitable functionalities, can be cyclized to give access to enantiomerically enriched 2-aryl-1,5-benzodioxepins.

New methods for the preparation of 1-phenyl-trans-cyclohexane-1,2-diol

Abstract In contrast with previous reports, it was found that the reaction of 1-phenylcyclohexene with peroxyformic acid is not entirely stereospecific, but gives some trans -1-phenylcyclohexane-1, 2-diol (IV) beside the cis -isomer (III). The reaction of 1-phenylcyclohexene oxide (II) with formic acid yielded a similar mixture of III and IV, while addition of trichloroacetic acid in benzene was entirely cis -stereospecific. Reaction of the epoxide II with potassium hydroxide took place only under very drastic conditions to give a small yield of III, while sodium 2-dimethylaminoethoxide added exclusively in a trans way, leading to the amino ether X, which was easily transformed into the trans -glycol IV. The latter compound was also the main product of the borohydride reduction of 2-hydroxy-2-phenylcyclohexanone (IX). Possible explanations of the observed stereochemical results are discussed.

Nickel-catalyzed borylative ring opening of vinyl epoxides and aziridines.

A mild ring opening of vinyl epoxides and aziridines with B(2)Pin(2) catalyzed by Ni(0)-Binap affords new functionalized allylic boron derivatives which undergo sequential transformations. The uncatalyzed allylation of aldehydes allows obtaining challenging bishomoallylic alicyclic 1,3-diols and 1,3-amino alcohols with remarkably high stereoselectivities. Valuable trans-bisallylic 1,4-amino alcohols can be obtained by a simple oxidation.

Regiochemical control of the ring opening of 1:2-epoxides by means of chelating processes. 10. Synthesis and ring opening reactions of mono- and difunctionalized cis and trans aliphatic oxirane systems

Abstract The regiochemical outcome of the ring opening of 1:2-epoxides through chelation processes assisted by metal ions, was verified in mono- and difunctionalized aliphatic oxirane systems bearing the heterofunctionality (OR) in an homoallylic and/or allylic relationship to the oxirane ring. The effect of the distance of the OR functionality from the oxirane ring and of the type of protective group on the regiochemical outcome of these systems is examined. In some cases, the use of LiClO4 or Mg(ClO4)2 as the promoting metal salt makes it possible the obtainment of a nice regioalternating process.