Organic Letters
Letter
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Negishi, E.-i. Zirconocene-promoted stereoselective bicyclization of
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(14) One should note that Zr-catalyzed carbomagnesation reactions
with 2 involving a β-heteroatom elimination have been reported.
Depending on the substrate, a β-heteroatom elimination from an
organozirconium or an organomagnesium intermediate was proposed.
See: (a) Didiuk, M. T.; Johannes, C. W.; Morken, J. P.; Hoveyda, A.
H. Enantio-, Diastereo-, and Regioselective Zirconium-Catalyzed
Carbomagnesiation of Cyclic Ethers with Higher Alkyls of
Magnesium. Utility in Synthesis and Mechanistic Implications. J.
Am. Chem. Soc. 1995, 117, 7097−7104. (b) Suzuki, N.; Kondakov, D.
Y.; Takahashi, T. Zirconium-catalyzed highly regioselective carbon-
carbon bond formation reactions. J. Am. Chem. Soc. 1993, 115, 8485−
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catalyzed asymmetric carbomagnesation. J. Am. Chem. Soc. 1993, 115,
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(15) (a) Zheng, J.; Lin, Y.; Liu, F.; Tan, H.; Wang, Y.; Tang, T.
Controlled Chain-Scission of Polybutadiene by the Schwartz
Hydrozirconation. Chem. - Eur. J. 2013, 19, 541−548. (b) Fujita,
K.; Nakamura, T.; Yorimitsu, H.; Oshima, K. Triethylborane-Induced
Radical Reaction with Schwartz Reagent. J. Am. Chem. Soc. 2001, 123,
3137−3138. (c) Negishi, E.-i.; Yoshida, T. A novel zirconium-
catalyzed hydroalumination of olefins. Tetrahedron Lett. 1980, 21,
1501−1504.
(16) 2-MeTHF was chosen to avoid undesired THF-opening. See:
Bailey, W. J.; Marktscheffel, F. Cleavage of Tetrahydrofuran during
Reductions with Lithium Aluminum Hydride. J. Org. Chem. 1960, 25,
1797−1800.
(17) For precedence of the in situ generation of 1, see: (a) Zhao, Y.;
Snieckus, V. A Practical in situ Generation of the Schwartz Reagent.
Reduction of Tertiary Amides to Aldehydes and Hydrozirconation.
Org. Lett. 2014, 16, 390−393. (b) Zhao, Y.; Snieckus, V. A. Schwartz
reagents: methods of in situ generation and use. United States Patent,
US 8,168,833 B2, 2012. (c) Huang, Z.; Negishi, E.-i. A Convenient
and genuine Equivalent to HZrCp2Cl Generated in Situ from
ZrCp2Cl2−DIBAL-H. Org. Lett. 2006, 8, 3675−3678.
(18) (a) Fuller, J. C.; Stangeland, E. L.; Jackson, T. C.; Singaram, B.
Lithium aluminum hydride-N-methylpyrrolidine complex. 1. Syn-
thesis and Reactivity of Lithium Aluminum Hydride-N-Methylpyrro-
lidine Complex. An Air and Thermally Stable Reducing Agent
Derived from Lithium Aluminum Hydride. Tetrahedron Lett. 1994,
35, 1515−1518. See also: (b) Marlett, E. M.; Park, W. S.
Dimethylamine alane and N-Methylpyrrolidine-Alane. A Convenient
Synthesis of Alane, a Useful Selective Reducing Agent in Organic
Synthesis. J. Org. Chem. 1990, 55, 2968−2969. (c) Ehrlich, R.; Rice,
G. The Chemistry of Alane. XII. The Lithium Tetrahydroalanate−
Triethylamine Complex. Inorg. Chem. 1966, 5, 1284−1286.
(19) Attempts to prepare and isolate LiAlH4·NMP according to the
literature procedure (ref 18a) were unsuccessful. Instead, literature-
known AlH3·2NMP was observed by NMR together with a second
(20) A Cp2TiCl2/LiAlH4 catalyzed C−O cleavage of allylic ethers
and other oxygenated molecules had been reported earlier, but it was
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(c) Gansauer, A.; Justicia, J.; Fan, C.-A.; Worgull, D.; Piestert, F.
Reductive C−C Bond Formation after Epoxide Opening via Electron
̈
Transfer. Top. Curr. Chem. 2007, 279, 25−52. (d) Gansauer, A.;
Lauterbach, T.; Narayan, S. Strained Heterocycles in Radical
Chemistry. Angew. Chem., Int. Ed. 2003, 42, 5556−5573.
(7) Selected references: (a) Biberger, T.; Makai, S.; Lian, Z.;
Morandi, B. Iron-Catalyzed Ring-Closing C−O/C−O Metathesis of
Aliphatic Ethers. Angew. Chem., Int. Ed. 2018, 57, 6940−6944.
(b) Lohr, T. L.; Li, Z.; Marks, T. J. Thermodynamic Strategies for C−
O Bond Formation and Cleavage via Tandem Catalysis. Acc. Chem.
Res. 2016, 49, 824−834. (c) Adduci, L. L.; McLaughlin, M. P.;
́
Bender, T. A.; Becker, J. J.; Gagne, M. R. Metal-Free Deoxygenation
of Carbohydrates. Angew. Chem., Int. Ed. 2014, 53, 1646−1649.
(d) Yang, J.; White, P. S.; Brookhart, M. Scope and Mechanism of the
Iridium-Catalyzed Cleavage of Alkyl Ethers with Triethylsilane. J. Am.
Chem. Soc. 2008, 130, 17509−17518. (e) Gevorgyan, V.; Rubin, M.;
Benson, S.; Liu, J.-X.; Yamamoto, Y. A Novel B(C6F5)3-Catalyzed
Reduction of Alcohols and Cleavage of Aryl and Alkyl Ethers with
Hydrosilanes. J. Org. Chem. 2000, 65, 6179−6186.
(8) Selected references: (a) Matsuda, T.; Shiose, S.; Suda, Y.
Rhodium-Catalyzed Double 1,4-Addition of Arylboronic Acids to β-
Aryloxyacrylates Involving β-Oxygen Elimination. Adv. Synth. Catal.
2011, 353, 1923−1926. (b) Zhao, H.; Ariafard, A.; Lin, Z. β-
Heteroatom versus β-Hydrogen Elimination: A Theoretical Study.
Organometallics 2006, 25, 812−819. (c) Lautens, M.; Fagnou, K.;
Hiebert, S. Transition Metal-Catalyzed Enantioselective Ring-Open-
ing Reactions of Oxabicyclic Alkenes. Acc. Chem. Res. 2003, 36, 48−
58. (d) Murakami, M.; Itahashi, T.; Amii, H.; Takahashi, K.; Ito, Y.
New Domino Sequences Involving Successive Cleavage of Carbon−
Carbon and Carbon−Oxygen Bonds: Discrete Product Selection
Dictated by Catalyst Ligands. J. Am. Chem. Soc. 1998, 120, 9949−
9950. (e) Henry, P. M. Palladium(II)-catalyzed exchange and
isomerization reactions. Acc. Chem. Res. 1973, 6, 16−24.
(9) Tran, V. T.; Gurak, J. A., Jr.; Yang, K. S.; Engle, K. M. Activation
of diverse carbon−heteroatom and carbon−carbon bonds via
palladium(II)-catalysed β-X elimination. Nat. Chem. 2018, 10,
1126−1133.
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(10) (a) Sommer, H.; Julia-Hernandez, F.; Martin, R.; Marek, I.
Walking Metals for Remote Functionalization. ACS Cent. Sci. 2018, 4,
153−165. (b) Marek, I.; Chinkov, N.; Levin, A. A Zirconium
Promenade - An Efficient Tool in Organic Synthesis. Synlett 2006,
501−514. (c) Annby, U.; Karlsson, S.; Gronowitz, S.; Hallberg, A.;
Alvhall, J.; Svenson, R. Hydrozirconation−Isomerization. Reactions of
Terminally Functionalized Olefins with Zirconocene Hydrides and
General Aspects. Acta Chem. Scand. 1993, 47, 425−433.
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(11) (a) Cenac, N.; Zablocka, M.; Igau, A.; Commenges, G.;
Majoral, J.-P.; Skowronska, A. Zirconium-Promoted Ring Opening.
Scope and Limitations. Organometallics 1996, 15, 1208−1217.
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(b) Cenac, N.; Zablocka, M.; Igau, A.; Majoral, J.-P.; Pietrusiewicz,
M. Zirconium-Promoted Ring Opening. A Useful New Methodology.
Organometallics 1994, 13, 5166−5168. (c) Karlsson, S.; Hallberg, A.;
Gronowitz, S. Hydrozirconation of oleyl alcohol. J. Am. Oil Chem. Soc.
1989, 66, 1815−1821 and cited references . (d) Buchwald, S. L.;
Nielsen, R. B.; Dewan, J. C. Synthesis, structure, and reaction of (1-
ethoxyethyl)zirconocene chloride, a stable acyclic secondary zircono-
cene alkyl. Organometallics 1988, 7, 2324−2328.
(12) For reviews on the chemistry of 1, see: (a) Wipf, P.; Jahn, H.
Synthetic applications of organochlorozirconocene complexes.
Tetrahedron 1996, 52, 12853−12910. (b) Majoral, J.-P.; Zablocka,
́
M.; Igau, A.; Cenac, N. Zirconium Species as Tools in Phosphorus
Chemistry, 1 [Cp2ZrHCl]n, a Versatile Reagent. Chem. Ber. 1996, 129,
879−886. For the original reports, see: (c) Hart, D. W.; Schwartz, J.
Hydrozirconation. Organic synthesis via organozirconium intermedi-
ates. Synthesis and rearrangement of alkylzirconium(IV) complexes
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E
Org. Lett. XXXX, XXX, XXX−XXX