Paolo Crotti

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.

Enzyme Fingerprints of Activity, and Stereo- and Enantioselectivity from Fluorogenic and Chromogenic Substrate Arrays

A series of stereochemically and structurally diverse fluorogenic and chromogenic substrates for hydrolytic enzymes has been synthesized and used to characterize enzyme activity profiles of esterases, lipases, proteases, peptidases, phosphatases, and epoxide hydrolases. The substrates used are particularly resilient to nonspecific reactions due to their mechanism of activation. The activities recorded with the individual substrates are therefore remarkably reproducible, and enable us to use the overall pattern of activity as a specific fingerprint for the enzyme sample. Fingerprints of activity, and enantio- and stereoselectivity are displayed as arrays of color-scale squares that are easily analyzed visually. Such fingerprints might be useful for quality control, enzyme discovery, and possibly for addressing the issue of functional convergence in enzymes.

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.

Regiochemical control of the ring opening of 1,2-epoxides by means of chelating processes. 8. Synthesis and ring opening reactions of cis- and trans- oxides derived from 3-benzyloxycyclohexene and 2-benzyloxy-5,6-dihydro-2H-pyran

Abstract The regiochemical outcome of the ring opening of 1,2-epoxides bearing polar remote functionalization through chelation processes assisted by metal ions, was verified in cyclic oxirane systems having the polar functionality in an allylic position to the oxirane ring. The diastereoisomeric cis/trans epoxide pairs 5,6 and 7,8 derived from 3-benzyloxycyclohexene, and 2-benzyloxy-5,6-dihydro-2H-pyran, respectively, were prepared and several of their opening reactions were studied. The regioselectivity observed largely depends on the reaction conditions (standard or metal-assisted) and, interestingly, on the nature of the nucleophile used.

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.

Synthesis and Ring-Opening Reactions of the Diastereoisomericcis- andtrans-Epoxides Derived from 3-(Benzyloxy)cyclopentene and 2-(Benzyloxy)-2,5-dihydrofuran

The regiochemical outcome of the ring-opening of epoxides bearing remote polar functionalities has been established in the case of carbocyclic (1 and 2) and the corresponding furanosidic (3 and 4) title epoxides. Under standard conditions, the regioisomeric C-1 products are the sole (from trans epoxides 2 and 4) or predominant (from cis epoxides 1 and 3) ring-opening products. However, under chelating conditions, and only in the case of the cis epoxides 1 and 3, a consistent increase in C-2 selectivity is unexpectedly observed.