Mechanistic Analysis and Characterization of Intermediates in the Phosphane-Catalyzed Oligomerization of Isocyanates

Julian Helberg; Yohei Oe; Hendrik Zipse

doi:10.1002/chem.201804016

Mechanistic Analysis and Characterization of Intermediates in the Phosphane-Catalyzed Oligomerization of Isocyanates

Chemistry. 2018 Sep 25;24(54):14387-14391. doi: 10.1002/chem.201804016. Epub 2018 Sep 3.

Authors

Julian Helberg¹, Yohei Oe², Hendrik Zipse¹

Affiliations

¹ Department of Chemistry, LMU München, Butenandtstrasse 5-13, 81377, München, Germany.
² Graduate School of Life and Medical Sciences, Department of Biomedical Information, Faculty of Life and Medical Sciences, Doshisha University, 1-3 Tatara Miyakodani, Kyotanabe, Kyoto, 610-0394, Japan.

PMID: 30085378
DOI: 10.1002/chem.201804016

Abstract

The mechanism of the oligomerization of aliphatic isocyanates catalyzed by trialkylphosphanes has been studied through low temperature ³¹ P and ¹⁵ N NMR spectroscopy combined with computational chemistry. A revised mechanism is proposed that contains several (spiro)cyclic pentacoordinate phosphorous intermediates. Previously reported spectroscopic data of a transient intermediate has been reevaluated and assigned to a cyclic intermediate containing a P-N bond by experiments with ¹⁵ N-labeled isocyanate. ¹³ C, ¹⁵ N, and ³¹ P NMR shifts that support this assignment have been calculated using quantum chemical methods.

Keywords: Lewis base organocatalysis; NMR spectroscopy; computational chemistry; isotopic labeling; reaction mechanisms.