N-Oxazolidinoyl Diene Iron(0) Tricarbonyl Complexes: Preparation By Diastereoselective Complexation And Synthetic Applications

Document Type

Article

Publication Date

8-8-2022

Published In

Organometallics

Abstract

We describe the synthesis of a family of chiral, nonracemic 3,4-disubstituted 2-N-oxazolidinoyl-1,3-dienes (10 and 15a–15i) via Stille–Fürstner coupling. These chiral dienes were converted to the corresponding iron(0) tricarbonyl complexes (11 and 16a–16i) with good to high diastereoselectivity (3:1 to >15:1). The combined chemical yields of these steps, as well as the complexation diastereoselectivities, were generally superior to the analogous chiral 2-sulfinyl-1,3-dienes we reported earlier. Stereochemical assignments of the diene iron(0) tricarbonyl complexes were facilitated by X-ray crystallography and circular dichroism, and a computational search for the lowest energy confirmation of 10 was undertaken to understand the origin of the complexation diastereoselectivity. Complexes 16b and 16e were each carried through synthetic pathways that included RCM to make an initial comparison of the reactivity of this family of diene iron tricarbonyl complexes with the previously reported sulfinyl-1,3-diene iron(0) tricarbonyl complexes. Sidechains of complexes 43 and 44 were each modified for introduction of an α-diazoester unit, and diastereoselective Rh₂(OAc)₄-catalyzed intramolecular C–H insertions were carried with to afford pentacyclic complexes 48 and 49. Demetallation of 48, subsequent elaboration of the oxazolidinoyl diene, and intramolecular aza-Michael gave fused N-Ts pyrrolidine 54 as a single diastereomer.

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