Synlett 2014; 25(14): 2072-2074
DOI: 10.1055/s-0034-1378496
letter
© Georg Thieme Verlag Stuttgart · New York

Proline-Catalyzed Dehydrogenative Cross-Coupling Reaction between Chromene and Aldehydes

Zi-Jun Wu
a   Department of Chemistry, Zhejiang University, Hangzhou 310028, P. R. of China
,
Jian Qian
b   Zhejiang Jianye Chemical Co. Ltd., Hangzhou, 311604, P. R. of China
,
Tian-Tian Wang
a   Department of Chemistry, Zhejiang University, Hangzhou 310028, P. R. of China
,
Zhi-Zhen Huang*
a   Department of Chemistry, Zhejiang University, Hangzhou 310028, P. R. of China
c   State Key Laboratory of Elemento-organic Chemistry, Nankai University, Tianjin 300071, P. R. of China   Fax: +86(571)88807077   eMail: huangzhizhen@zju.edu.cn
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Publikationsverlauf

Received: 30. April 2014

Accepted after revision: 14. Juni 2014

Publikationsdatum:
16. Juli 2014 (online)


Abstract

An unprecedented DCC reaction between chromene and aldehydes catalyzed by proline has been developed via direct C–H functionalization. A plausible mechanism using DDQ to activate α-C–H of chromene and proline to activate aldehyde is also proposed.

Supporting Information

 
  • References and Notes

  • 4 Clausen DJ, Floreancig PE. J. Org. Chem. 2012; 77: 6574
  • 5 Rueping M, Volla CM. R, Atodiresei L. Org. Lett. 2012; 14: 4642
  • 6 Sperry J, Wilson ZE, Rathwell DC. K, Brimble MA. Nat. Prod. Rep. 2010; 27: 1117
  • 7 LiClO4 may promote the conversion of chromene to oxocarbenium ion pair and 4 Å MS may prevent the formation of ether dimers. For details, see ref. 4.
  • 8 2H-Chromenyl alcohols 3 are more stable than the products of the DCC reaction.
  • 9 Under the optimized conditions, the ee values of the two diastereomers of 3a are about 22%.
  • 10 General Procedure for the DCC Reaction of Chromene (1) with Aldehyde 2a–i, Followed by Reduction for 3a–i: Under nitrogen, the mixture of chromene (1; 39.6 mg, 0.3 mmol), LiClO4 (38.16 mg, 0.36 mmol), 4 Å MS (75 mg), DDQ (81.72 mg, 0.36 mmol) was stirred for 0.5 h in freshly distilled MeCN (2 mL) at 0 °C. Then aldehyde 2 (0.9 mmol) and l-proline (6.9 mg, 0.06 mmol) were added, and the reaction mixture was stirred for 24 h at r.t. (about 20 °C). After evaporation of the solvent under reduced pressure, NaBH4 (37.83 mg, 1.0 mmol) and EtOH (2 mL) were added to the mixture. The reaction mixture was stirred for 2 h at 0 °C. Then H2O (10 mL) was added, and the mixture was extracted with EtOAc (3 × 10 mL). The combined organic layer was dried over Na2SO4 and evaporated. The residue was purified by column chromatography (silica gel; PE–EtOAc, 1:10 or 1:20) to give the desired product 3.