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DFT Study on the Sn II ‐Catalyzed Diastereoselective Synthesis of Tetrahydrofuran from D–A Cyclopropane and Benzaldehyde
Author(s) -
Zhang Jinsheng,
Shen Wei,
Li Ming
Publication year - 2007
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.200700216
Subject(s) - cyclopropane , chemistry , benzaldehyde , tetrahydrofuran , natural bond orbital , medicinal chemistry , catalysis , photochemistry , computational chemistry , density functional theory , organic chemistry , solvent , ring (chemistry)
By means of density functional theory (DFT), the regio‐ and diastereoselective mechanism for the synthesis of 2,5‐disubstituted tetrahydrofuran from a donor–acceptor (D–A) cyclopropane cycloaddition reaction with benzaldehyde catalyzed by Sn(OTf) 2 was investigated. As demonstrated, the overall reaction includes the activation of the D–A cyclopropane ( S )‐ 1 , an unusual S N 2 attack on the activated cyclopropane, the formation of the tetrahydrofuran coordination complex and the regeneration of the catalyst. The D –A cyclopropane is activated by its combination with Sn(OTf) 2 , which leads to a decrease in the natural bond orbital (NBO) energy ofσ* (C1–C2) and an increase in the dipole moment and angular deviation of the bent bond σ (C1–C2) . Two nucleophilic reactions generates two chiral carbon centres, and the first one is rate controlling. In the S N 2 reaction, one molecule of trifluoromethane sulfonate forms a hydrogen‐bond H (CHO) ··· O (OTf) , which can control the stretching direction of the benzaldehyde. On the whole, the solvation energies of the species increase with increases in the molecular dipole moments, and the solvent effects increase the reaction barriers. The theoretically predicted dominant product is cis ‐(2 R ,5 R )‐tetrahydrofuran. So these can satisfactorily account for the experimental observations.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)