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Origins of Selectivity for the [2+2] Cycloaddition of α,β-unsaturated Ketones within a Porous Self-assembled Organic Framework

Yang, Jun and Dewal, Mahender B. and Profeta, Salvatore, Jr. and Smith, Mark D. and Li, Youyong and Shimizu, Linda S. (2008) Origins of Selectivity for the [2+2] Cycloaddition of α,β-unsaturated Ketones within a Porous Self-assembled Organic Framework. Journal of the American Chemical Society, 130 (2). pp. 612-621. ISSN 0002-7863. https://resolver.caltech.edu/CaltechAUTHORS:20170512-165844816

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Abstract

This article studies the origins of selectivity for the [2+2] cycloadditions of α,β-unsaturated ketones within a porous crystalline host. The host, formed by the self-assembly of a bis-urea macrocycle, contains accessible channels of ∼6 Å diameter and forms stable inclusion complexes with a variety of cyclic and acyclic α,β-unsaturated ketone derivatives. Host 1 crystals provide a robust confined reaction environment for the highly selective [2+2] cycloaddition of 3-methyl-2-cyclopentenone, 2-cyclohexenone, and 2-methyl-2-cyclopentenone, forming their respective exo head-to-tail dimers in high conversion. The products are readily extracted from the self-assembled host and the crystalline host can be efficiently recovered and reused. Molecular modeling studies indicate that the origin of the observed selectivity is due to the excellent match between the size and shape of these guests to dimensions of the host channel and to the preorganization of neighboring enones into favorable reaction geometries. Small substrates, such as acrylic acid and methylvinylketone, were bound by the host and were protected from photoreactions. Larger substrates, such as 4,4-dimethyl-2-cyclohexenone and mesityl oxide, do not undergo selective [2+2] cycloaddition reactions. In an effort to understand these differences in reactivity, we examined these host−guest complexes by thermogravimetric analysis (TGA), NMR, powder X-ray diffraction (PXRD) and molecular modeling.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1021/ja076001+DOIArticle
http://pubs.acs.org/doi/abs/10.1021/ja076001%2BPublisherArticle
http://pubs.acs.org/doi/suppl/10.1021/ja076001%2BPublisherSupporting Information
ORCID:
AuthorORCID
Yang, Jun0000-0001-8701-9297
Li, Youyong0000-0002-5248-2756
Additional Information:© 2008 American Chemical Society. Received 9 August 2007. Published online 21 December 2007. Published in print 1 January 2008. This work was supported by the NSF (CHE-071817), by the Petroleum Research Fund (44682), and by a grant from the University of South Carolina, Office of Research and Health Sciences Research Funding Program.
Funders:
Funding AgencyGrant Number
NSFCHE-071817
American Chemical Society Petroleum Research Fund44682
University of South CarolinaUNSPECIFIED
Issue or Number:2
Record Number:CaltechAUTHORS:20170512-165844816
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20170512-165844816
Official Citation:Origins of Selectivity for the [2+2] Cycloaddition of α,β-unsaturated Ketones within a Porous Self-assembled Organic Framework Jun Yang, Mahender B. Dewal, Salvatore Profeta, Jr., Mark D. Smith, Youyong Li, and Linda S. Shimizu Journal of the American Chemical Society 2008 130 (2), 612-621 DOI: 10.1021/ja076001+
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:77435
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:16 May 2017 19:45
Last Modified:09 Mar 2020 13:19

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