Reactivity and Stereoselectivity in the Inverse-Electron-Demand Diels–Alder Reaction of 1-Aza-1,3-Butadiene

TL;DR

This paper studies a chemical reaction using theory to understand how different groups affect the reaction's speed and product shape.

Contribution

The study reveals new insights into how specific functional groups influence reaction selectivity and reactivity.

Findings

The C−C bond forms first due to electron delocalization, determining regioselectivity.

Endo selectivity is driven by orbital interactions, electrostatics, and dispersion.

Functional groups like sulfonyl and methoxycarbonyl affect selectivity differently.

Abstract

The reactivity and stereoselectivity in the inverse-electron-demand Diels–Alder reaction between 4-methoxycarbonyl-N-(phenylsulfonyl)-1-aza-1,3-butadiene and methoxyethene was examined using density functional theory (DFT) calculations at the M06-2X level. The formation of the two bonds in this reaction was calculated to be asynchronous. The formation of the C−C bond occurs first and is driven by electron delocalization from the dienophile to the diene, a process which simultaneously governs the regioselectivity. Moreover, the endo selectivity of the reaction was found to arise from non-bonding-orbital interactions, electrostatic attractions, and dispersion interactions. The sulfonyl group attached to the diene influences the selectivity and the reactivity. In contrast, when a methoxycarbonyl group is attached to the diene, it affects the selectivity in a different way depending on the position where it is attached.

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