This reaction also affords (C5H5)2ZrH2, which is treated with methylene chloride to give Schwartz's reagent [3]
An alternative procedure that generated Schwartz's reagent from dihydride has also been reported.[4] Moreover, it's possible to perform an in situ preparation of (C5H5)2ZrHCl from zirconocene dichloride by using LiH. This method can also be used to synthesize isotope-labeled molecules, like olefines by employing Li2H or Li3H as reducing agents.[5]
Schwartz's reagent has a low solubility in common organic solvents.[6] The trifluoromethanesulfonate (C5H5)2ZrH(OTf) is soluble in THF.[7]
Structureedit
The complex adopts the usual "clam-shell" structure seen for other Cp2MXn complexes.[8] The dimetallic structure has been confirmed by Microcrystal electron diffraction.[9] The results are consistent with FT-IR spectroscopy, which established that the hydrides are bridging. Solid state NMR spectroscopy also indicates a dimeric structure. The X-ray crystallographic structure for the methyl compound (C5H5)4Zr2H2(CH3)2 compound is analogous.[10]
Computational studies indicate that hydrozirconation occurs from the interior portion.[19][20]
When treated with one equivalent of Cp2ZrClH, diphenylacetylene gives the corresponding alkenylzirconium as a mixture of cis and trans isomers. With two equivalents of hydride, the endproduct was a mixture of erythro and threo zircono alkanes:
The corresponding organoboron and organoaluminum compounds were already known, but these are air-sensitive and/or pyrophoric whereas organozirconium compounds are not.
One example of a one-pot hydrozirconation - carbonylation - coupling is depicted below:[24][25]
With certain allyl alcohols, the alcohol group is replaced by nucleophilic carbon forming a cyclopropane ring:[26] The selectivity of the hydrozirconation of alkynes has been studied in detail.[27][28] Generally, the addition of the Zr–H proceeds via the syn-addition. The rate of addition to unsaturated carbon-carbon bonds is terminal alkyne > terminal alkene ≈ internal alkyne > disubstituted alkene [29]Acyl complexes can be generated by insertion of CO into the C–Zr bond resulting from hydrozirconation.[30] Upon alkene insertion into the zirconium hydride bond, the resulting zirconium alkyl undergoes facile rearrangement to the terminal alkyl and therefore only terminal acyl compounds can be synthesized in this way. The rearrangement most likely proceeds via β-hydride elimination followed by reinsertion.
Further readingedit
Hart, D. W.; Schwartz, J. (1974). "Hydrozirconation. Organic Synthesis via Organozirconium Intermediates. Synthesis and Rearrangement of Alkylzirconium(IV) Complexes and Their Reaction with Electrophiles". J. Am. Chem. Soc.96 (26): 8115–8116. doi:10.1021/ja00833a048.
Schwartz, J.; Labinger, J. A. (2003). "Hydrozirconation: A New Transition Metal Reagent for Organic Synthesis". Angew. Chem. Int. Ed.15 (6): 330–340. doi:10.1002/anie.197603331.
Hart, Donald W.; Blackburn, Thomas F.; Schwartz, Jeffrey (1975). "Hydrozirconation. III. Stereospecific and regioselective functionalization of alkylacetylenes via vinylzirconium(IV) intermediates". J. Am. Chem. Soc.97 (3): 679–680. doi:10.1021/ja00836a056.
Referencesedit
^Pinheiro, Danielle L. J.; De Castro, Pedro P.; Amarante, Giovanni W. (2018). "Recent Developments and Synthetic Applications of Nucleophilic Zirconocene Complexes from Schwartz's Reagent". European Journal of Organic Chemistry. 2018 (35): 4828–4844. doi:10.1002/ejoc.201800852. S2CID 102770378.
^Wailes, P. C.; Weigold, H. (1970). "Hydrido complexes of zirconium I. Preparation". J. Organomet. Chem.24 (2): 405–411. doi:10.1016/S0022-328X(00)80281-8.
^Buchwald, Stephen L.; LaMaire, Susan J.; Nielsen, Ralph B.; Watson, Brett T.; King, Susan M. (1993). "Schwartz's Reagent". Org. Syntheses. 71: 77. doi:10.15227/orgsyn.071.0077.
^Wipf, Peter; Takahashi, Hidenori; Zhuang, Nian (1998). "Kinetic vs. thermodynamic control in hydrozirconation reactions" (PDF). Pure Appl. Chem.70 (5): 1077–1082. doi:10.1351/pac199870051077. S2CID 94092883.
^Zippi, E. M.; Andres, H.; Morimoto, H.; Williams, P. G. (1994-04-01). "Preparation and Use of Tritiated Schwartz' Reagent (ZrCp2Cl3H)". Synthetic Communications. 24 (7): 1037–1044. doi:10.1080/00397919408020780. ISSN 0039-7911.
^Luinstra, Gerrit A.; Rief, Ursula; Prosenc, Marc H. (1995-04-01). "Synthesis and Reactivity of Cp2ZrH(OSO2CF3), a Soluble Monomeric Alternative for Schwartz's Reagent, and the Solid-State Structure of Its Dimer, [Cp2Zr(OSO2CF3)(-H)]2.0.5THF". Organometallics. 14 (4): 1551–1552. doi:10.1021/om00004a003. ISSN 0276-7333.
^Jones, Christopher G.; Asay, Matthew; Kim, Lee Joon; Kleinsasser, Jack F.; Saha, Ambarneil; Fulton, Tyler J.; Berkley, Kevin R.; Cascio, Duilio; Malyutin, Andrey G.; Conley, Matthew P.; Stoltz, Brian M.; Lavallo, Vincent; Rodríguez, José A.; Nelson, Hosea M. (6 September 2019). "Characterization of Reactive Organometallic Species via MicroED". ACS Central Science. 5 (9): 1507–1513. doi:10.1021/acscentsci.9b00403. PMC6764211. PMID 31572777.
^Rossini, A. J.; Mills, R. W.; Briscoe, G. A.; Norton, E. L.; Geier, S. J.; Hung, I.; Zheng, S.; Autschbach, J.; Schurko, R. W. (2009). "Solid-State Chlorine NMR of Group IV Transition Metal Organometallic Complexes". Journal of the American Chemical Society. 131 (9): 3317–3330. doi:10.1021/ja808390a. PMID 19256569.
^Leighty, M. W.; Spletstoser, J. T.; Georg, Gunda I. (2011). "Mild Conversion of Tertiary Amides to Aldehydes Using Cp2ZrHCl (Schwartz's Reagent)". Org. Synth.88: 427–437. doi:10.1002/0471264229.os088.39. ISBN 978-0471264224.
^Li, H.; Walsh, P. J. (2005). "Catalytic Asymmetric Vinylation and Dienylation of Ketones". J. Am. Chem. Soc.127 (23): 8355–8361. doi:10.1021/ja0425740. PMID 15941269.
^Duffey, Matthew O.; Le Tiran, Arnaud; Morken, James P. (2003). "Enantioselective Total Synthesis of Borrelidin". J. Am. Chem. Soc. 125 (6): 1458–1459. doi:10.1021/ja028941u. PMID 12568588.
^Wu, J.; Panek, J. S. (2011). "Total Synthesis of (−)-Virginiamycin M2: Application of Crotylsilanes Accessed by Enantioselective Rh(II) or Cu(I) Promoted Carbenoid Si–H Insertion". J. Org. Chem. 76 (24): 9900–9918. doi:10.1021/jo202119p. PMID 22070230.
^Hu, T.; Panek, J. S. (1999). "Total Synthesis of (−)-Motuporin". J. Org. Chem. 64 (9): 3000–3001. doi:10.1021/jo9904617. PMID 11674393.
^Nicolaou, K. C.; et al. (2003). "Total Synthesis of Apoptolidin: Completion of the Synthesis and Analogue Synthesis and Evaluation". J. Am. Chem. Soc. 125 (50): 15443–15454. doi:10.1021/ja030496v. PMID 14664590.
^"Allylic alcohols by alkene transfer from zirconium to zinc: 1-[(tert-butyldiphenylsilyl)oxy]-dec-3-en-5-ol". Organic Syntheses. 9 (74): 205. 1998. Retrieved 2013-03-23. Organic Syntheses, Coll. Vol. 9, p.143 (1998); Vol. 74, p.205 (1997).
^Conjugate Addition Of A Vinylzirconium Reagent: 3-(1-Octen-1-Yl)Cyclopentanone, Organic Syntheses, Coll. Vol. 9, p.640 (1998); Vol. 71, p.83 (1993).
^Pankratyev, E. Y.; Tyumkina, T. V.; Parfenova, L. V.; Khursan, S. L.; Khalilov, L. M.; Dzhemilev, U. M. (2011). "DFT and Ab Initio Study on Mechanism of Olefin Hydroalumination by XAlBui2 in the Presence of Cp2ZrCl2 Catalyst. II.(1) Olefin Interaction with Catalytically Active Centers". Organometallics. 30 (22): 6078–6089. doi:10.1021/om200518h.
^Wang, Juping; Xu, Huiying; Gao, Hui; Su, Cheng-Yong; Zhao, Cunyuan; Phillips, David Lee (2010). "DFT Study on the Mechanism of Amides to Aldehydes Using Cp2Zr(H)Cl". Organometallics. 29 (1): 42–51. doi:10.1021/om900371u.
^Hart, D. W.; Schwartz, J. (1974). "Hydrozirconation. Organic Synthesis via Organozirconium Intermediates. Synthesis and Rearrangement of Alkylzirconium(1V) Complexes and Their Reaction with Electrophiles". Journal of the American Chemical Society. 96 (26): 8115–8116. doi:10.1021/ja00833a048.
^Zhang, Donghui (2007). "Directed Hydrozirconation of Propargylic Alcohols". Journal of the American Chemical Society. 129 (40): 12088–12089. doi:10.1021/ja075215o. PMC2669288. PMID 17850152.
^Kang, Suk-Ku (2002). "Palladium-catalyzed coupling reaction of acylzirconocene chlorides with hypervalent iodonium salts: synthesis of aryl-substituted ketones". Journal of the Chemical Society, Perkin Transactions 1 (4): 459–461. doi:10.1039/b110983a.
^Gandon, Vincent (2002). "A one-pot access to cyclopropanes from allylic ethers via hydrozirconation–deoxygenative ring formation". Chemical Communications (12): 1308–1309. doi:10.1039/b203762a. PMID 12109129.
^Sun, R. C.; Okabe, M.; Coffen, D. L.; Schwartz, J. (1998). "Conjugate Addition of a Vinylzirconium Reagent: 3-(1-Octene-1-yl)cyclopentanone". Organic Syntheses; Collected Volumes, vol. 9, p. 640.
^Panek, J. S.; Hu, T. (1997). "Stereo- and Regiocontrolled Synthesis of Branched Trisubstituted Conjugated Dienes by Palladium(0)-Catalyzed Cross-Coupling Reaction". J. Org. Chem.62 (15): 4912–4913. doi:10.1021/jo970647a.
^Bertelo, Christopher A.; Schwartz, Jeffrey (1975). "Hydrozirconation. II. Oxidative homologation of olefins via carbon monoxide insertion into the carbon-zirconium bond". J. Am. Chem. Soc.97 (1): 228–230. doi:10.1021/ja00834a061.
External linksedit
Wikimedia Commons has media related to Schwartz's reagent.
Examples in organic synthesis at the University of Connecticut website