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Garner P, Cox PB, Anderson JT, et al. Use of Silicon-Based Tethers to Control Diastereofacial Selectivity in Azomethine Ylide Cycloadditions(1). J Org Chem. 1997;62(3):493-498doi: 10.1021/jo9609034.
Garner, P., Cox, P. B., Anderson, J. T., Protasiewicz, J., & Zaniewski, R. (1997). Use of Silicon-Based Tethers to Control Diastereofacial Selectivity in Azomethine Ylide Cycloadditions(1). The Journal of organic chemistry, 62(3), 493-498. https://doi.org/10.1021/jo9609034
Garner, Philip, et al. "Use of Silicon-Based Tethers to Control Diastereofacial Selectivity in Azomethine Ylide Cycloadditions(1)." The Journal of organic chemistry vol. 62,3 (1997): 493-498. doi: https://doi.org/10.1021/jo9609034
Garner P, Cox PB, Anderson JT, Protasiewicz J, Zaniewski R. Use of Silicon-Based Tethers to Control Diastereofacial Selectivity in Azomethine Ylide Cycloadditions(1). J Org Chem. 1997 Feb 07;62(3):493-498. doi: 10.1021/jo9609034. PMID: 11671439.
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J Org Chem. 1997 Feb 07;62(3):493-498. doi: 10.1021/jo9609034.

Use of Silicon-Based Tethers to Control Diastereofacial Selectivity in Azomethine Ylide Cycloadditions(1).

The Journal of organic chemistry

Philip Garner, Philip B. Cox, James T. Anderson, John Protasiewicz, Rebecca Zaniewski

Affiliations

  1. Department of Chemistry, Case Western Reserve University, Cleveland, Ohio 44106-7078.

PMID: 11671439 DOI: 10.1021/jo9609034

Abstract

A novel approach to controlling the diastereofacial selectivity of intramolecular dipolar cycloadditions of azomethine ylides (cf. 9 --> 8) by varying the structure a silicon-based tether is described. A correlation is found between the length of the tether dipolarophile conjugate (TDC) and the observed sense of diastereocontrol. Azomethine ylides incorporating longer [OSiPh(2)OCH(2)CH(2)OCOCH=CH(2)], [OSi(i-Pr)(2)OSi(i-Pr)(2)OCH(2)CH=CH(2)], and [OSiPh(2)OCH(2)CH=CH(2)] TDCs favor endo-si attack (14 --> 16, 19 --> 20, and 21 --> 22) while the shorter TDC [OSiR(2)CH(2)CH=CH(2)] leads to a reversal in selectivity favoring the endo-re product (23a,b --> 24a,b). Structures of the cycloadducts have been assigned on the basis of selected X-ray diffraction data in combination with chemical/spectral correlation experiments. The work described herein represents a conceptually new approach to stereocontrol and extends the use of silicon-based tethers in asymmetric synthesis.

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