51
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Procopio A, Dalpozzo R, De Nino A, Maiuolo L, Nardi M, Tagarelli A. Er(OTf) 3as a Mild Cleaving Agents for Acetals and Ketals. SYNTHESIS-STUTTGART 2004. [DOI: 10.1055/s-2004-815941] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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52
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Bartoli G, Bosco M, Dalpozzo R, Marcantoni E, Massaccesi M, Sambri L. Zn(ClO4)2·6H2O as a Powerful Catalyst for a Practical Acylation of Alcohols with Acid Anhydrides. European J Org Chem 2003. [DOI: 10.1002/ejoc.200300458] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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53
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Dalpozzo R, De Nino A, Maiuolo L, Procopio A, Nardi M, Bartoli G, Romeo R. Highly efficient and versatile acetylation of alcohols catalyzed by cerium(III) triflate. Tetrahedron Lett 2003. [DOI: 10.1016/s0040-4039(03)01358-3] [Citation(s) in RCA: 102] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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54
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Cupone G, Nino AD, Dalpozzo R, Maiuolo L, Procopio A, Sindona G. The formation of symmetrical glycosyl glycuronates by direct oxidation of partially protected methyl α-D-glycopyranosides. ARKIVOC 2002. [DOI: 10.3998/ark.5550190.0003.b12] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
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55
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Dalpozzo R, De Nino A, Maiuolo L, Procopio A, Tagarelli A, Sindona G, Bartoli G. Simple and efficient chemoselective mild deprotection of acetals and ketals using cerium(III) triflate. J Org Chem 2002; 67:9093-5. [PMID: 12467437 DOI: 10.1021/jo0260387] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A new and chemoselective method for the cleavage of alkyl and cyclic acetals and ketals at room temperature in wet nitromethane by using catalytic cerium(III) trifluoromethane sulfonate is presented. The high yields, the observed selectivity, the very gentle reaction conditions, and the almost neutral pH make this procedure particularly attractive for multistep synthesis.
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56
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Bartoli G, Bosco M, Dalpozzo R, Giuliani A, Marcantoni E, Mecozzi T, Sambri L, Torregiani E. An efficient procedure for the preparation of (E)-alpha-alkylidenecycloalkanones mediated by a CeCl(3) x 7H(2)O-NaI system. Novel methodology for the synthesis of (S)-(-)-pulegone. J Org Chem 2002; 67:9111-4. [PMID: 12467442 DOI: 10.1021/jo026418s] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
2-Alkylidenecycloalkanones are powerful synthons used as the key intermediates in many important syntheses. Because of their potential, a general method of preparation from readily available starting materials, under very mild conditions, was considered to be worthwhile. Cerium(III) chloride heptahydrate in combination with sodium iodide in refluxing acetonitrile promotes a regio- and stereoselective beta-elimination reaction to (E)-2-alkylidenecycloalkanones in 2-(1-hydroxyalkyl)cycloalkanones. The synthetic value of the present procedure is demonstrated by the synthesis of monoterpene (S)-(-)-pulegone (8) in its optically active form.
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Bartoli G, Cupone G, Dalpozzo R, De Nino A, Maiuolo L, Procopio A, Tagarelli A. Stereoselective reduction of enaminones to syn γ-aminoalcohols. Tetrahedron Lett 2002. [DOI: 10.1016/s0040-4039(02)01545-9] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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58
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De Nino A, Dalpozzo R, Cupone G, Maiuolo L, Procopio A, Tagarelli A, Bartoli G. Stereoselective Complete Reduction of α-Alkyl-β-ketonitriles toanti γ-Amino Alcohols. European J Org Chem 2002. [DOI: 10.1002/1099-0690(200209)2002:17<2924::aid-ejoc2924>3.0.co;2-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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59
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Bartoli G, Cupone G, Dalpozzo R, De Nino A, Maiuolo L, Procopio A, Sambri L, Tagarelli A. Deprotection of t-butyldimethylsilyl ethers promoted by cerium(IV) triflate. Tetrahedron Lett 2002. [DOI: 10.1016/s0040-4039(02)01254-6] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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60
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Bartoli G, Bosco M, Cimarelli C, Dalpozzo R, De Munno G, Guercio G, Palmieri G. Reaction of dianions of acyclic .beta.-enamino ketones with electrophiles. 3. Nitriles: synthesis of pyridine and pyrimidine derivatives. J Org Chem 2002. [DOI: 10.1021/jo00048a043] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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61
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Bartoli G, Bosco M, Dalpozzo R, Todesco PE. Functionalization of aromatic systems: a highly chemoselective synthesis of trimethylsilylmethylnitroarenes. J Org Chem 2002. [DOI: 10.1021/jo00369a025] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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62
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Bartoli G, Marcantoni E, Petrini M, Dalpozzo R. Reaction of aryl and alkyl nitro compounds with 2-butenylmagnesium chloride: synthesis of a new class of nitrones. J Org Chem 2002. [DOI: 10.1021/jo00301a046] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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63
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Bartoli G, Bosco M, Caretti D, Dalpozzo R, Todesco PE. Highly chemoselective addition of (o-nitrobenzyl)silanes to nonenolizable aldehydes. J Org Chem 2002. [DOI: 10.1021/jo00228a043] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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64
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Bartoli G, Bosco M, Dalpozzo R, Marcantoni E, Massaccesi M, Rinaldi S, Sambri L. Mg(ClO4)2as a Powerful Catalyst for the Acylation of Alcohols under Solvent-Free Conditions. Synlett 2002. [DOI: 10.1055/s-2003-36228] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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65
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Bartoli G, Dalpozzo R, De Nino A, Procopio A, Sambri L, Tagarelli A. Addition of organocerium reagents to homoallyl alcohols. Tetrahedron Lett 2001. [DOI: 10.1016/s0040-4039(01)01917-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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66
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Dalpozzo R, Bartoli G, Bosco M, De Nino A, Procopio A, Sambri L, Tagarelli A. An Efficient Diastereoselective Reduction of α-Alkyl-β-keto Carbonitriles with TiCl4/BH3 or LiBH4/CeCl3 to syn- or anti-α-Alkyl-β-hydroxy Carbonitriles. European J Org Chem 2001. [DOI: 10.1002/1099-0690(200108)2001:15<2971::aid-ejoc2971>3.0.co;2-k] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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67
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Troiano P, Oldani A, Gozzini C, Iraci M, Dalpozzo R, Baratta M, De Mattia M. Latanoprost 0.005%: evaluation of its effect on accommodative capacity. ACTA OPHTHALMOLOGICA SCANDINAVICA. SUPPLEMENT 2001:52-4. [PMID: 11235537 DOI: 10.1111/j.1600-0420.2000.tb01104.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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68
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Bartoli G, Cupone G, Dalpozzo R, De Nino A, Maiuolo L, Marcantoni E, Procopio A. Cerium-Mediated Deprotection of Substituted Allyl Ethers. Synlett 2001. [DOI: 10.1055/s-2001-18746] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
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69
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Bartoli G, Bellucci MC, Bosco M, Dalpozzo R, Marcantoni E, Sambri L. The role of the alpha-stereogenic center in the control of stereoselection in the reduction of alpha-alkyl-beta-hydroxy ketones: a highly diastereoselective protocol for the synthesis of 1,2-syn-2-alkyl-1,3-diols. Chemistry 2000; 6:2590-8. [PMID: 10961404 DOI: 10.1002/1521-3765(20000717)6:14<2590::aid-chem2590>3.0.co;2-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Accurate investigations on the role played by an alpha-stereogenic center in controlling the reduction of various classes of beta-hydroxy ketones allowed us to set up a general and highly diastereoselective protocol for the synthesis of 2-alkyl-1,3-diols with 1,2-syn relationship. This methodology is based on the conversion of a beta-hydroxy ketone into the corresponding titanium alcoholate that permits us to organize the substrate in a stable and rigid structure, which stereofacially favors attacking hydride ions. The use of THF as solvent makes available a variety of hydride donors that cover a large spectrum of steric demand: the choice of the more appropriate one depends on the conformational stability of the cyclic intermediate. Excellent results are obtained also in the presence of an additional stereogenic center in the beta-position, even if it exerts a concordant or an opposite steric effect with respect to the alpha-substituent.
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70
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Dalpozzo R, De Nino A, Miele D, Procopio A, Tagarelli A, Bartoli G. Dianions of acyclic β-enamino ketones and electrophiles. 9. Synthesis and reactivity of phosphorylated enaminones. HETEROATOM CHEMISTRY 2000. [DOI: 10.1002/(sici)1098-1071(2000)11:1<1::aid-hc1>3.0.co;2-u] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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71
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72
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Bartoli G, Bellucci MC, Bosco M, Dalpozzo R, De Nino A, Sambri L, Tagarelli A. Mechanism and Extensibility of the Reaction. European J Org Chem 2000. [DOI: 10.1002/(sici)1099-0690(200001)2000:1<99::aid-ejoc99>3.0.co;2-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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73
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Dalpozzo R, De Nino A, Miele D, Tagarelli A, Bartoli G. Synthesis of Phosphane Oxides and Phosphonates by Cerium-Mediated Addition of Organolithium Compounds to Chloro-Phosphorus Compounds. European J Org Chem 1999. [DOI: 10.1002/(sici)1099-0690(199909)1999:9<2299::aid-ejoc2299>3.0.co;2-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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74
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Cundari S, Dalpozzo R, De Nino A, Procopio A, Sindona G, Athanassopulos K. A facile one-pot synthesis of the very useful building blocks N-Boc-S-alkylatedcysteines. Tetrahedron 1999. [DOI: 10.1016/s0040-4020(99)00528-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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75
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Marcantoni E, Alessandrini S, Malavolta M, Bartoli G, Bellucci MC, Sambri L, Dalpozzo R. Reversed Stereochemical Control in the Presence of CeCl(3) and TiCl(4) in the Lewis Acid Mediated Reduction of alpha-Alkyl-beta-keto Esters by Metal Hydrides. A General Methodology for the Diastereoselective Synthesis of syn- and anti-alpha-Alkyl-beta-hydroxy Esters. J Org Chem 1999; 64:1986-1992. [PMID: 11674293 DOI: 10.1021/jo9821574] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The Lewis acid-mediated reduction of alpha-alkyl-beta-keto esters has been shown to proceed by different stereochemical control depending on the nature of the metal atom. Strongly chelating TiCl(4) led to the syn isomer in high diastereomeric excess in noncoordinating solvents (CH(2)Cl(2)) at -78 degrees C with BH(3).py as reducing agent, while nonchelating CeCl(3) gave a high excess of the anti isomer in coordinating solvents (THF) at the same temperature with lithium triethylborohydride (LiEt(3)BH) as reducing agent. The methodology has been successfully utilized for obtaining important syn- and anti-alpha-alkyl-beta-hydroxy esters with high diastereoselectivity.
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