Subscribe to RSS
DOI: 10.1055/s-2003-42098
The CeCl3·nH2O/NaI System in Organic Synthesis: An Efficient Water Tolerant Lewis Acid Promoter
Publication History
Publication Date:
15 October 2003 (online)
Abstract
The ability of CeCl3·nH2O/NaI system to work as an useful water tolerant promoter and/or reagent in many organic transformations is reviewed. They include Michael additions of 1,3-dicarbonyl compounds, amines and indoles to α,β-unsaturated ketones, and related systems, the cleavage of carbon-oxygen and carbon-silicon bonds, the conversion of alcohols into the corresponding iodides, as well as the stereospecific dehydration of β-hydroxy carbonyl compounds and the hydroxacyclization of unsaturated 3-hydroxy esters. Generally the reactions are carried out at reflux in wet CH3CN, however, in some case, it is possible to work under solvent free conditions and/or in the presence of the catalyst supported on SiO2. In the last case the simple experimental procedures allow the complete recovery of the catalyst and its recycling without loss of activity. Many of these protocols found wide application in organic synthesis and are now methods of common choice, since they are competitive and in some cases superior to the pre-existing procedures. The reasons for this success can be ascribed to the fact that this reagent allows the reaction to be carried out in close to neutral conditions and thus allows the survival of a large variety of functionalities sensitive to acidic hydrolysis. In addition, CeCl3·7H2O and NaI are cheap, non toxic, and stable compounds, and therefore the protocols based on their use represent an environmentally benign alternative to current chemical processes using water intolerant Lewis acids.
-
1 Introduction
-
2 Michael Additions
-
3 Cleavage of Carbon-Oxygen and Silicon-Oxygen Bonds
-
3.1 General Protocol for the Deprotection of PMB Ethers
-
3.2 Cleavage of Trityl, Trialkylsilyl, and Allyl Ethers
-
3.3 Cleavage of tert-Butyl and Prenyl Esters
-
3.4 Deprotection of Dioxolanes, Oxathiolanes, and Dithiolanes
-
4 Reactions Involving the Hydroxyl Group
-
4.1 Conversion of Alcohols into Iodides
-
4.2 Dehydration of β-Hydroxy Carbonylic Compounds to the
Corresponding α,β-Unsaturated Derivatives -
4.3 Synthesis of E-Alkylidene Cycloalkanones
-
4.4 Hydroxacyclization of Unsaturated 3-Hydroxy Esters
-
5 The Origin of the High Lewis Acid Activity of
CeCl3·nH2O/NaI Combination -
6 Conclusions
Key words
cerium(III) chloride - Lewis acids - sodium iodide - Michael additions - cleavage of ethers - hydroxyl group transformation
-
1a
Anastas PT.Warner JC. Green Chemistry: Theory and Practice Oxford University Press; New York: 1998. - 1b Special Topic Issue on Green Chemistry: Pure Appl. Chem. 2000, 72: 1207
- 1c Special Topic Issue on Green Chemistry: Acc. Chem. Res. 2002, 35: 1207
-
1d
Eissen M.Metzger JO.Schmidt E.Schneidewind U. Angew. Chem. Int. Ed. 2002, 41: 414 -
2a
Matlack AS. Introduction to Green Chemistry Marcel Dekker; New York: 2001. p.137 -
2b
Lewis Acid Reagents: A Practical Approach
Yamamoto H. Oxford Press; New York: 1999. -
2c
Santelli M.Pons J.-M. Lewis Acids and Selectivity in Organic Synthesis CRC Press; Boca Raton: 1995. -
3a
Imamoto T. In Comprehensive Organic Synthesis Vol. 4:Trost BM.Fleming I.Screiber SL. Pergamon Press; Oxford: 1991. p.231-250 -
3b
Imamoto T. Lanthanides in Organic Synthesis Academic Press; New York: 1994. -
3c
Stell PG. J. Chem. Soc., Perkin Trans. 1 2001, 2727 -
3d
Kagan HB.Namy JL. Tetrahedron 1986, 42: 6573 -
4a
Pearson RG. J. Am. Chem. Soc. 1963, 85: 3533 -
4b
Pearson RG. Science 1966, 151: 172 -
4c
Parr RG.Pearson RG. J. Am. Chem. Soc. 1983, 105: 7512 -
4d
Pearson RG. J. Chem. Educ. 1987, 64: 561 - CeCl3·7H2O is the key component of the Luche reduction:
-
5a
Luche JL. J. Am. Chem. Soc. 1978, 100: 2226 -
5b
Luche JL.Rodriguez-Ham L.Crabbe P. J. Chem. Soc., Chem. Commun. 1978, 601 -
5c
Gemal AL.Luche JL. J. Am. Chem. Soc. 1981, 103: 5454 -
5d
Warren S.Clayden J. Angew. Chem., Int. Ed. Engl. 1996, 35: 241 - For a recent use of CeCl3·7H2O as Lewis acid see:
-
6a
Christoffers J.Werner T.Unger S.Frey W. Eur. J. Org. Chem. 2003, 425 -
6b
Muñoz-Muñiz O.Quintanar-Audelo M.Juaristi E. J. Org. Chem. 2003, 68: 1622 -
6c
Martelli G.Morri S.Savoia D. Synlett 2002, 158 -
6d
Fiore K.Martelli G.Monari M.Savoia D. Tetrahedron: Asymmetry 1999, 10: 4803 -
6e
El-Shehawy AA.Omara MA.Ito K.Itsuno S. Synlett 1998, 367 -
6f
Xiao X.Bai D. Synlett 2001, 535 -
6g
Ankala SV.Fenteany G. Tetrahedron Lett. 2002, 43: 4729 -
6h
Bose DS.Fatima L.Mereyala HB. J. Org. Chem. 2003, 68: 587 -
6i
Babu RS. Synlett 2002, 1935 - Dry CeCl3 is used for the preparation of organocerium compounds. For example see:
-
7a
Imamoto T.Kusumoto T.Tawarayama Y.Sugiura Y.Mita T.Hatanaka Y.Yokoyama M. J. Org. Chem. 1984, 49: 3904 -
7b
Imamoto T.Sugiura Y.Takiyama N. Tetrahedron Lett. 1984, 25: 4233 -
7c
Imamoto T.Takiyama N.Nakamura K.Hatajima T.Kamiya Y. J. Am. Chem. Soc. 1989, 111: 4392 -
7d
Bartoli G.Marcantoni E.Petrini M. Angew. Chem., Int. Ed. Engl. 1993, 32: 1061 -
7e
Bartoli G.Marcantoni E.Petrini M. J. Chem. Soc., Chem. Commun. 1993, 1373 -
7f
Bartoli G.Marcantoni E.Sambri L.Tamburini M. Angew. Chem., Int. Ed. Engl. 1995, 32: 2046 -
7g
Liu HJ.Shia KS.Shang X.Zhu BY. Tetrahedron 1999, 55: 3803 - Dry CeCl3 is employed in stereoselective reduction of functionalized ketones:
-
8a
Bartoli G.Marcantoni E.Bosco M.Dalpozzo R.Sambri L. Chem.-Eur. J. 1997, 3: 1941 -
8b
Bartoli G.Marcantoni E.Bosco M.Cingolani S.Sambri L. J. Org. Chem. 1998, 63: 3624 -
8c
Bartoli G.Bellucci MC.Alessandrini S.Malavolta M.Marcantoni E.Sambri L. J. Org. Chem. 1999, 64: 1986 -
8d
Dalpozzo R.Bartoli G.Bosco M.De Nino A.Procopio A.Sambri L.Tagarelli A. Eur. J. Org. Chem. 2001, 4: 2971 - 9
Kobayashi S.Busujima T.Nagayama S. Chem.-Eur. J. 2000, 6: 3491 - 10
Sabitha G.Babu RS.Rajkumar M.Srividya R.Yadav JS. Org. Lett. 2001, 3: 1149 - 11
Bartoli G.Bosco M.Sambri L.Marcantoni E.Nobili F. J. Org. Chem. 1997, 62: 4183 - 12
Bartoli G.Bellucci MC.Bosco M.Marcantoni E.Sambri L.Torregiani E. Eur. J. Org. Chem. 1999, 617 - 13
Duval D.Geribaldi S. The Chemistry of Enones Part 1Patai S.Rappoport Z. Interscience; New York: 1989. p.335-405 - 14
Talay P.De Long MJ.Procheska HJ. Proc. Natl. Acad. Sci. U.S.A. 1988, 85: 8261 - 15
Christoffers J. J. Chem. Soc., Perkin Trans. 1 1997, 3141 - 16
Kobayashi S. Synlett 1994, 689 - 17
Christoffers J. Eur. J. Org. Chem. 1998, 1259 ; and references therein - 19
Bartoli G.Bosco M.Marcantoni E.Petrini M.Sambri L.Torregiani E. J. Org. Chem. 2001, 66: 9052 - These compounds are versatile intermediates for natural products antibiotics and chiral auxiliares. For example see:
-
20a
Bartoli G.Cimarelli C.Marcantoni E.Palmieri G.Petrini M. J. Org. Chem. 1994, 59: 5328 ; and references therein -
20b
Wang Y.-F.Izawa T.Kobayashi S.Ohno M. J. Am. Chem. Soc. 1982, 104: 6465 - 20c Hashiguchi S., Kawada A., Natsugari H.; J. Chem. Soc., Perkin Trans. 1; 1991, 2435
-
20d
Senanayake CH.Fang K.Grover P.Bakale RP.Vandenbassche CP.Wald SA. Tetrahedron Lett. 1999, 40: 819 -
20e
Genov M.Dimitrov V.Ivanova V. Tetrahedron: Asymmetry 1997, 8: 3703 -
20f
Hayashi Y.Rohde JJ.Corey EJ. J. Am. Chem. Soc. 1996, 118: 5502 -
20g
Eliel EL.He X.-C. J. Org. Chem. 1990, 55: 2114 - 21
Toda F.Takumi H.Nagami M.Tanaka K. Heterocycles 1998, 47: 469 - For recent reports on Michael additions catalyzed by friendly Lewis acids see:
-
22a
Yadav JS.Geetha V.Subba Reddy BV. Synth. Commun. 2002, 32: 3519 -
22b
Srivastava N.Banik BK. J. Org. Chem. 2003, 68: 2109 - 24
Bartoli G.Bartolacci M.Bosco M.Foglia G.Giuliani A.Marcantoni E.Sambri L.Torregiani E. J. Org. Chem. 2003, 68: 4594 -
25a
Bandini M.Cozzi PG.Giacomini M.Melchiorre P.Selva S.Umani-Ronchi A. J. Org. Chem. 2002, 67: 3700 -
25b
Yadav JS.Abraham S.Subba Reddy BV.Sabitha G. Tetrahedron Lett. 2001, 42: 8063 -
25c
Yadav JS.Abraham S.Subba Reddy BV.Sabitha G. Synthesis 2001, 2165 -
25d
Manabe K.Aoyama N.Kobayashi S. Adv. Synth. Catal. 2001, 174 -
25e
Harrington PE.Kerr MA. Synlett 1996, 1047 -
25f
Yadav JS.Reddy BVS.Murthy VSR.Mahesh KG.Madan C. Synthesis 2001, 783 -
25g
Jensen KB.Thorhange J.Hazel RG.Jørgensen KA. Angew. Chem. Int. Ed. 2001, 40: 160 -
25h
Zhuang W.Hansen T.Jørgensen KA. Chem. Commun. 2001, 347 -
25i
Bandini M.Cozzi PG.Melchiorre P.Umani-Ronchi A. J. Org. Chem. 2002, 67: 5386 ; and references therein - 26
Bartoli G.Marcantoni E.Sambri L. Seminars in Organic Synthesis XXV Summer School ‘A. Corbella’ Gargnano (BS), Italian Chemical Society; Rome: 2000. p.117-138 - 27
Bartoli G.Bellucci MC.Bosco M.Cappa A.Marcantoni E.Sambri L.Torregiani E. J. Org. Chem. 1999, 64: 5696 - For recent methods of selective cleavage of PMB-ethers under mild conditions see:
-
28a
Kim JD.Han G.Zee OP.Jung YH. Tetrahedron Lett. 2003, 44: 733 -
28b
Dalpozzo R.De Nino A.Maiuolo L.Procopio A.Tagarelli A.Sindona G.Bartoli G. J. Org. Chem. 2002, 67: 9093 -
28c
Barone G.Bedini E.Iadonisi A.Manzo E.Parrilli M. Synlett 2002, 1645 -
28d
Falck JR.Barma DK.Baati R.Mioskowski C. Angew. Chem. Int. Ed. 2001, 40: 1281 -
28e
Yu W.Su M.Gao X.Yang Z.Jin Z. Tetrahedron Lett. 2000, 41: 4015 -
28f
Yadav JS.Subba Reddy BV.Madan CH.Riaz Hashim S. Chem. Lett. 2000, 738 - 29
Montalban AG.Wittenberg LO.McKillop A. Tetrahedron Lett. 1999, 40: 5893 - 30 The CeCl3·nH2O/NaI system is able to cleave THP ethers only in protic solvents such as MeOH or MeOH/H2O:
Reddy GS.Neelakantan P.Iyengar DS. Synth. Commun. 2000, 30: 4107 - For the ring opening of oxiranes and aziridines by CeCl3·nH2O/NaI combination see:
-
31a
Reddy RL.Reddy MA.Bhanumathi N.Rama Rao K. Synthesis 2001, 831 -
31b
Sabitha G.Babu RS.Rajkumar M.Reddy CS.Yadav JS. Tetrahedron Lett. 2001, 42: 3955 - 32
Bartoli G.Bosco M.Marcantoni E.Sambri L.Torregiani E. Synlett 1998, 209 - For recent methods of selective deprotection of silyl ethers under mild conditions see:
-
33a
Bartoli G.Cupone G.Dalpozzo G.De Nino A.Maiuolo L.Procopio A.Sambri L.Tagarelli A. Tetrahedron Lett. 2002, 43: 5945 -
33b
Chen MY.Lu KC.Lee ASY.Lin CC. Tetrahedron Lett. 2002, 43: 2777 -
33c
Gopinath R.Patel BK. Org. Lett. 2000, 2: 4177 -
33d
Yadav JS.Reddy BVS.Madan C. New J. Chem. 2000, 24: 853 -
33e
Yu Z.Verkade JG. J. Org. Chem. 2000, 65: 2065 -
33f
Sabitha G.Syamala M.Yadav JS. Org. Lett. 1999, 1: 1701 -
33g
Saravanan P.Singh VK. J. Indian Chem. Soc., Sect. B 1998, 75: 565 -
33h
Hunter R.Hinz W.Richards P. Tetrahedron Lett. 1999, 40: 3643 -
33i
Ranu BC.Jana U.Majee A. Tetrahedron Lett. 1999, 40: 1985 -
34a In order to rule out the hypothesis of a reaction proceeding through a redox process the desilylation was carried out in the presence of 2,6-di-tert-butyl-4-methylphenol as a radical inhibitor:
Janzen EG.Wilcox AL.Manoharan V. J. Org. Chem. 1993, 58: 3597 -
34b
As expected the reaction occurred smoothly indicating that the mechanism could not involve electron transfer processes.
-
34c
Molander GA. Chem. Rev. 1992, 92: 29 -
34d
Hwu JR.Jain ML.Tsai F.-Y.Balakumar A.Hakimelahi GH. J. Org. Chem. 2000, 65: 5077 - 35
Yokokawa F.Inaizumi A.Shioiri T. Tetrahedron Lett. 2001, 42: 5903 - 36
Yadav JS.Reddy BVS. Synlett 2000, 1275 - 37 Thomas R. M., Reddy G. S., Iyengar D. S.; Tetrahedron Lett.; 1999, 40: 7293
- 38
Dalpozzo R.Cupone G.De Nino A.Maiuolo L.Procopio A.Marcantoni E.Bartoli G. Synlett 2001, 1897 -
39a
Lin LS.Lanza T.de Laszlo SE.Truong Q.Kamenecka T.Hagmann WK. Tetrahedron Lett. 2000, 41: 7013 -
39b
Tamaki M.Han G.Hruby VC. J. Org. Chem. 2001, 66: 3593 -
39c
Gibson FS.Bergmeier SC.Rapoport H. J. Org. Chem. 1994, 59: 3216 -
39d
Routier S.Saugé L.Ayerbe N.Coudert G.Mérour J.-Y. Tetrahedron Lett. 2002, 43: 589 -
39e
Grieco PA.Hon YS.Perez-Medrano A. J. Am. Chem. Soc. 1988, 110: 1630 -
39f
Baldwin JE.Adlington RM.Godfrey CRA.Gollins DW.Schofield CJ. Tetrahedron 1991, 47: 5835 - 40
Wu Y.Limburg DC.Wilkinson DE.Vaal MJ.Hamilton GS. Tetrahedron Lett. 2000, 41: 2847 - 41
Yadav JS.Subba Reddy BV.Venkateshwara Rao C.Chand PK.Prasad AR. Synlett 2002, 137 - 42
Yadav JS.Reddy BVS.Raghavendra S.Satyanarayana M. Tetrahedron Lett. 2002, 43: 4679 -
43a
Fukuzawa S.Tsuruta T.Fujinami T.Sakai S. J. Chem. Soc., Perkin Trans. 1 1987, 1473 -
43b
Fukuzawa S.Fujinami T.Sakai S. J. Chem. Soc., Chem. Commun. 1985, 777 - 44
Lavilla R.Coll O.Nicolas M.Sufi BA.Torrents J.Bosch J. Eur. J. Org. Chem. 1999, 2997 - 45
Carreño MC.Garcia-Cerrada S.Urbano A. J. Am. Chem. Soc. 2001, 123: 7929 - 46
Wang S.Chen G.Kayser M.Iwaki H.Lau PCK.Hasegawa Y. Can. J. Chem. 2001, 613 -
47a
Descoins C.Thanh GV.Boyer FD.Ducrot PH.Descoins C.Lallemand JY. Synlett 1999, 240 -
47b
Descoins CL.Thanh GV.Boyer FD.Ducrot PH.Prangé T.Descoins C. Eur. J. Org. Chem. 2003, 1172 - 48
Barrero AF.Cuerva JM.Manzaneda EJA.Oltra E.Chahboun R. Tetrahedron Lett. 2002, 43: 2793 - 49
Bartoli G.Bosco M.Dalpozzo R.Giuliani A.Marcantoni E.Mecozzi T.Sambri L.Torregiani E. J. Org. Chem. 2002, 67: 9111 - 50
Arjona O.Menchaca R.Plumet J. Org. Lett. 2001, 3: 107 - 51
Keller L.Dumas F.d’Angelo J. Tetrahedron Lett. 2001, 42: 1911 - 52 CeCl3·nH2O/NaI is also used in the regeneration of alcohols from toluene sulfonates:
Reddy GS.Mohan GH.Iyengar DS. Synth. Commun. 2000, 30: 3829 - 53 In addition it has been reported that CeCl3·nH2O/NaI is able to perform chemoselective dealkylation of some aryl ethers:
Yadav JS.Subba Reddy BV.Madan CH.Riaz Hashim S. Chem. Lett. 2000, 738 -
54a
Kocie PJ. Protecting Groups Thieme Verlag; Stuttgart: 2000.ski -
54b
Greene TW.Wuts PGM. Protective Groups in Organic, Synthesis 3rd ed.: John Wiley & Sons; New York: 1999. -
54c
Kocie PJ.ski Jarowicki K. J. Chem. Soc., Perkin Trans. 1 2000, 2495 -
54d
Kocie PJ.ski Jarowicki K. J. Chem. Soc., Perkin Trans. 1 2001, 2109 - For some examples see:
-
55a
Hajipour AR.Mallakpour SE.Mohammadpoor-Baltrok I.Adibi H. Molecules 2002, 7: 674 -
55b
Mirjalili BF.Zolfigol MA.Bamoniri A. Russ. J. Org. Chem. 2002, 38: 761 -
55c
Hajipour AR.Aghajari MSE.Mohammadpoor-Baltrok I. Synth. Commun. 2002, 1311 -
55d
Hajipour AR.Mallakpour SE.Mohammadpoor-Baltrok I.Khoee S. Synth. Commun. 2002, 611 - 56
Bartoli G.Bellucci MC.Bosco M.Di Deo M.Marcantoni E.Sambri L.Torregiani E. J. Org. Chem. 2000, 65: 2830 - 57
Hagiwara H.Takeuchi F.Hoshi T.Suzuki T.Ando M. Tetrahedron Lett. 2001, 42: 7629 - 58
Bartoli G.Bellucci MC.Marcantoni E.Petrini M.Sambri L.Torregiani E. Org. Lett. 2000, 2: 1791 - 59
Bartoli G.Bellucci MC.Bosco M.Marcantoni E.Massaccesi M.Petrini M.Sambri L. J. Org. Chem. 2000, 65: 4553 -
60a
Paris JM.Barriere JC.Smith C.Bost PE. In Recent Progress in the Chemical Synthesis of AntibioticsLucas G.Ohno M. Springer-Verlag; Berlin: 1990. p.183-248 -
60b
Di Giambattista M.Chinali G.Cocito C. J. Antimicrob. Chemother. 1989, 24: 485 -
60c
Cocito C. Microbiol. Rev. 1979, 43: 145 - 61
Dvorak CA.Schmitz WD.Poon DJ.Pryde DC.Lawson JP.Amos RA.Meyers AI. Angew. Chem. Int. Ed. 2000, 39: 1664 -
62a
Ijima A.Takahashi K. Chem. Pharm. Bull. 1973, 21: 215 -
62b
Ksander GM.McMurry JE.Johnson M. J. Org. Chem. 1977, 42: 1180 -
62c
Renvers JTA.De Groot A. Synthesis 1982, 1105 -
62d
Nakano T.Irifune S.Umano S.Inada A.Ishii Y.Ogawa M. J. Org. Chem. 1987, 52: 2239 -
62e
Enholm EJ.Whitley PE.Xie Y. J. Org. Chem. 1996, 61: 5384 -
62f
Clive DLJ.Huang X. Tetrahedron 2001, 57: 3845 - 63
Conia J.-M.Amice P. Bull. Soc. Chim. Fr. 1970, 2972 - 64
Liebeskind LS.Chidambaram R.Mitchell D. Pure Appl. Chem. 1988, 60: 27 ; and references therein - 65
Ebenezer WJ.Wight P. In Comprehensive Organic Functional Group TransformationKatritzky AR.Meth-Cohn O.Rees CW. Pergamon Press; Oxford: 1995. Vol. 3. p.219-220 -
66a
Buschmann H.Scharf H.-D. Synthesis 1988, 827 -
66b
Wartheu JD.Lee C.-J.Jang EB.Lance DR.Mcinnis DO. J. Chem. Ecol. 1997, 23: 1891 -
66c Differences between (R)-pulegone and (S)-pulegone in methabolism in mammals are known too:
Madyastha KM.Geikwad NW. Xenobiotica 1998, 28: 723 - 67
Marotta E.Foresti E.Marcelli T.Peri F.Righi P.Scardovi N.Rosini G. Org. Lett. 2002, 4: 4451 - For recent reviews see:
-
68a
Faulkner DJ. Nat. Prod. Rep. 2001, 18: 1 -
68b
Koert U. Synthesis 1995, 115 -
68c
Harmange JC.Figadere B. Tetrahedron: Asymmetry 1993, 4: 1711 -
68d
Boivin TLB. Tetrahedron 1987, 43: 3309 - 69
Yadav JS.Reddy BVS.Reddy KB.Satyanarayana M. Tetrahedron Lett. 2002, 43: 7009 - 70
Sabesan S.Neira S. J. Org. Chem. 1991, 56: 5468 -
71a
Bolitt V.Mioskowski C.Lee SG.Falck JR. J. Org. Chem. 1990, 55: 5812 -
71b
Toshima K.Nagai H.Ushiki Y.Matsumura S. Synlett 1998, 1007 -
71c
Pachamuthu K.Vankar YD. J. Org. Chem. 2001, 66: 7511 -
72a
Ferrier RJ.Prasad NJ. J. Chem. Soc. C 1969, 570 -
72b
Ferrier RJ. Adv. Carbohydr. Chem. Biochem. 1969, 24: 199 -
72c
Masson C.Soto J.Bessodes M. Synlett 2000, 1281 -
73a
Le Roux C.Gaspard-Iloughmane H.Dubac J. J. Bull. Soc. Chim. Fr. 1993, 130: 832 -
73b
Le Roux C.Dubac J. Synlett 2002, 181 - 74
Le Roux C.Gaspard-Iloughmane H.Dubac J. J. Org. Chem. 1993, 58: 1835 - 75
Olah GA.Narang SC. Tetrahedron 1982, 38: 2225 -
77a
Shibasaki M.Sasai H.Arai T. Angew. Chem., Int. Ed. Engl. 1997, 36: 1236 -
77b
Kobayashi S.Sugiura M.Kitagawa H.Lam WW.-L. Chem. Rev. 2002, 102: 2227
References
A typical procedure follows. A flask was charge in succession with the 1, 3-dicarbonyl compound (1 equiv), the Michael acceptor (1.1 equiv), CeCl3·7H2O (0.2 equiv) and NaI (0.1 equiv). The mixture was then stirred at room temperature until the 1,3-dicarbonyl compound was consumed. The reaction was treated under stirring with Et2O (20 mL). The catalyst mixture was removed by filtration and reused. The organic layer was concentrated under reduced pressure and the crude product was purified by silica gel chromatography.
23Typical experimental procedure. Silica gel (30-60 µm 0.63 g) was added to a mixture of CeCl3·7H2O (13.6 mmol) and NaI (11.6 mmol) in CH3CN (50 mL), and the mixture was stirred overnight at room temperature. The CH3CN was removed by rotary evaporation and to the resulting reagent was added dibenzylamine (10 mmol) and methyl vinyl ketone (12.6 mmol). The mixture was stirred at 35 °C. After completion of the reaction and addition of Et2O the supported catalyst was recovered by filtration and reused. The organic layer was washed with 10% aqueous citric acid with aqueous saturated NaHCO3 solution dried over anhydrous Na2SO4 and the solvent evaporated under reduced pressure. The crude was purified by flash chromatography on SiO2 to give the corresponding β-amino derivative.
76Bartoli, G.; Bosco, M.; Giuliani, A.; Marcantoni, E.; Palmieri, A.; Petrini, M.; Sambri, L. Organomet. submitted for publication.