Catellani reaction

The Catellani reaction was discovered by Marta Catellani (Università degli Studi di Parma, Italy) and co-workers in 1997.[1][2] The reaction uses aryl iodides to perform bi- or tri-functionalization, including C-H functionalization of the unsubstituted ortho position(s), followed a terminating cross-coupling reaction at the ipso position. This cross-coupling cascade reaction depends on the ortho-directing transient mediator, norbornene.

Original and general reaction conditions for the Catellani reaction. PNP2 = cis,exo-2-phenylnorbornyl palladium chloride dimer

Reaction mechanism

The Catellani reaction is catalyzed by palladium and norbornene, although in most cases superstochiometric amounts of norbornene to deduce reaction time.[3] Palladium(0) oxidatively inserts in to aryl-iodide bond. Once carbopallation with the norbornene, the structure of the norbornylpalladium intermediate does not allow for ß-hydride elimination in either of the ß-positions due to Bredt's Rule over bridgehead proton and the trans-configuration of the palladium and ß-proton.[4] Thereafter, the Pd(II) species undergoes electrophilic cyclopalladation at the ortho position. The second oxidative addition occurs with the corresponding coupling partner to form a Pd(IV) intermediate, which then reductively eliminates and completes the first cross-coupling bond formation. After the elimination of norbornene, the Pd(II) species undergoes the second cross-coupling reaction, terminating the series with a number of traditional palladium-catalyzed coupling reactions.[5]

Catalytic cycle of the Catellani reaction.[6] (Ligands and stereochemistry are omitted for clarity.)

Steps of the Catellani reaction:

  1. Oxidative addition
  2. Carbopalladation of norbornene
  3. Palladacycle formation
  4. Oxidative addition to palladacycle
  5. Reductive elimination from palladacycle
  6. Norbornene extrusion
  7. Termination via Heck reaction, Suzuki reaction, etc.

Ortho and ipso cross-coupling partners

The Catellani reaction facilitates a variety of C—C and C—N bond-forming reactions at the ortho position. These include alkylation from alkyl halides,[1] arylation from aryl bromides,[7] amination from benzyloxyamines,[8][9][10][11] acylation from anhydrides.[12][13] Likewise in the case of terminating ipso coupling partners with Heck-type termination with olefins,[1] Suzuki-type reaction with boronic esters,[8] borylation with bis(pinacolato)diboron,[9] protonation with i-PrOH,[10] decarboxylative alkynylation with alkynyl carboxylic acids.[11]

Uses

With tethered cross-coupling partners, Lautens, Malacria, and Catellani used this reaction to construct a variety of fused ring systems since 2000.[5] The Catellani reaction has been used as a key step for the total synthesis (+)-linoxepin,[14] rhazinal,[15] aspidospermidine,[16] and (±)-goniomitine.[16]

References

  1. 1 2 3 Catellani, Marta; Frignani, Franco; Rangoni, Armando (1997-02-03). "A Complex Catalytic Cycle Leading to a Regioselective Synthesis of o,o′-Disubstituted Vinylarenes". Angewandte Chemie International Edition in English. 36 (1-2): 119–122. doi:10.1002/anie.199701191. ISSN 1521-3773.
  2. ↑ Catellani; et al. (1997). "Regioselektive Synthese o,o′-disubstituierter Vinylarene über einen komplexen Katalysecyclus". Angewandte Chemie. 109 (1-2). doi:10.1002/ange.19971090146. Retrieved 26 December 2014.
  3. ↑ Catellani, Marta; Motti, Elena; Della Ca’, Nicola (2008-11-18). "Catalytic Sequential Reactions Involving Palladacycle-Directed Aryl Coupling Steps". Accounts of Chemical Research. 41 (11): 1512–1522. doi:10.1021/ar800040u. ISSN 0001-4842.
  4. ↑ Martins; et al. (2010). "Synthesis in the Key of Catellani: Norbornene-Mediated ortho C–H Functionalization". Top Curr Chem. 292. doi:10.1007/128_2009_13. Retrieved 25 November 2015.
  5. 1 2 Ye, Juntao; Lautens, Mark. "Palladium-catalysed norbornene-mediated C–H functionalization of arenes". Nature Chemistry. 7 (11): 863–870. doi:10.1038/nchem.2372.
  6. ↑ Martins; et al. (2010). "Synthesis in the Key of Catellani: Norbornene-Mediated ortho C–H Functionalization". Top Curr Chem. 292. doi:10.1007/128_2009_13. Retrieved 25 November 2015.
  7. ↑ Faccini, Fiorenza; Motti, Elena; Catellani, Marta (2004-01-01). "A New Reaction Sequence Involving Palladium-Catalyzed Unsymmetrical Aryl Coupling". Journal of the American Chemical Society. 126 (1): 78–79. doi:10.1021/ja039043g. ISSN 0002-7863.
  8. 1 2 Ye, Changqing; Zhu, Hui; Chen, Zhiyuan (2014-09-19). "Synthesis of Biaryl Tertiary Amines through Pd/Norbornene Joint Catalysis in a Remote C–H Amination/Suzuki Coupling Reaction". The Journal of Organic Chemistry. 79 (18): 8900–8905. doi:10.1021/jo501544h. ISSN 0022-3263.
  9. 1 2 Shi, Hang; Babinski, David J.; Ritter, Tobias (2015-03-25). "Modular C–H Functionalization Cascade of Aryl Iodides". Journal of the American Chemical Society. 137 (11): 3775–3778. doi:10.1021/jacs.5b01082. ISSN 0002-7863.
  10. 1 2 Dong, Zhe; Dong, Guangbin (2013-12-11). "Ortho vs Ipso: Site-Selective Pd and Norbornene-Catalyzed Arene C–H Amination Using Aryl Halides". Journal of the American Chemical Society. 135 (49): 18350–18353. doi:10.1021/ja410823e. ISSN 0002-7863.
  11. 1 2 Sun, Fenggang; Gu, Zhenhua (2015-05-01). "Decarboxylative Alkynyl Termination of Palladium-Catalyzed Catellani Reaction: A Facile Synthesis of α-Alkynyl Anilines via Ortho C–H Amination and Alkynylation". Organic Letters. 17 (9): 2222–2225. doi:10.1021/acs.orglett.5b00830. ISSN 1523-7060.
  12. ↑ Huang, Yunze; Zhu, Rui; Zhao, Kun; Gu, Zhenhua (2015-10-19). "Palladium-Catalyzed Catellani ortho-Acylation Reaction: An Efficient and Regiospecific Synthesis of Diaryl Ketones". Angewandte Chemie International Edition. 54 (43): 12669–12672. doi:10.1002/anie.201506446. ISSN 1521-3773.
  13. ↑ Zhou, Ping-Xin; Ye, Yu-Ying; Liu, Ce; Zhao, Lian-Biao; Hou, Jian-Ye; Chen, Dao-Qian; Tang, Qian; Wang, An-Qi; Zhang, Jie-Yu (2015-08-07). "Palladium-Catalyzed Acylation/Alkenylation of Aryl Iodide: A Domino Approach Based on the Catellani–Lautens Reaction". ACS Catalysis. 5 (8): 4927–4931. doi:10.1021/acscatal.5b00516.
  14. ↑ Weinstabl; et al. (16 Apr 2013). "Total Synthesis of (+)-Linoxepin by Utilizing the Catellani Reaction". Angewandte Chemie International Edition. 52 (20). doi:10.1002/anie.201302327. Retrieved 26 December 2014.
  15. ↑ Sui; et al. (June 2013). "Pd-Catalyzed Chemoselective Catellani Ortho-Arylation of Iodopyrroles: Rapid Total Synthesis of Rhazinal". J. Am. Chem. Soc. 135 (25): 9318–9321. doi:10.1021/ja404494u. Retrieved 26 December 2014.
  16. 1 2 Jiao, Lei; Herdtweck, Eberhardt; Bach, Thorsten (2012-09-05). "Pd(II)-Catalyzed Regioselective 2-Alkylation of Indoles via a Norbornene-Mediated C–H Activation: Mechanism and Applications". Journal of the American Chemical Society. 134 (35): 14563–14572. doi:10.1021/ja3058138. ISSN 0002-7863.

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