Organocatalysis in Synthesis: L-Proline as an Enantioselective Catalyst in the Synthesis of Pyrans and Thiopyrans

doi:10.3390/molecules17044300

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Molecules 2012, 17(4), 4300-4312; doi:10.3390/molecules17044300

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Organocatalysis in Synthesis: L-Proline as an Enantioselective Catalyst in the Synthesis of Pyrans and Thiopyrans

Noha M. Hilmy Elnagdi* and Noura Saad Al-Hokbany

Women Students-Medical Studies & Sciences Sections, Chemistry Department, College of Science, King Saud University, Riyadh, KSA, P.O. Box 22452, Riyadh 11495, Saudi Arabia

* Author to whom correspondence should be addressed.

Received: 26 January 2012; in revised form: 19 March 2012 / Accepted: 20 March 2012 / Published: 10 April 2012

(This article belongs to the Special Issue Organocatalysis)

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Abstract: The multicomponent reaction (MCR) of aromatic aldehydes 1 and malononitrile (2) with active methylenes 5a–h in the presence of L-proline produced pyrans and thiopyrans 6a–h stereospecifically and in good yields. Moreover a novel MCR of ethyl propiolate (8) with 1 and 2 in the presence of L-proline to afford (R)-polysubstituted pyran is also reported. X-ray structures, e.e. and optical activity of the synthesized compounds indicated that L-proline as a catalyst is responsible for the observed enantioselectivity in the studied reactions.

Keywords: L-proline; pyran; assymetric synthesis; enantioselectivity; ethyl propiolate; optical activity

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MDPI and ACS Style

Elnagdi, N.M.H.; Al-Hokbany, N.S. Organocatalysis in Synthesis: L-Proline as an Enantioselective Catalyst in the Synthesis of Pyrans and Thiopyrans. Molecules 2012, 17, 4300-4312.

AMA Style

Elnagdi NMH, Al-Hokbany NS. Organocatalysis in Synthesis: L-Proline as an Enantioselective Catalyst in the Synthesis of Pyrans and Thiopyrans. Molecules. 2012; 17(4):4300-4312.

Chicago/Turabian Style

Elnagdi, Noha M. Hilmy; Al-Hokbany, Noura Saad. 2012. "Organocatalysis in Synthesis: L-Proline as an Enantioselective Catalyst in the Synthesis of Pyrans and Thiopyrans." Molecules 17, no. 4: 4300-4312.

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