Direct, biomimetic synthesis of (+)-artemone via a stereoselective, organocatalytic cyclization

We present a four-step synthesis of (+)-artemone from (–)- linalool, featuring iminium organocatalysis of a doubly diastereoselective conjugate addition reaction. The strategy follows a proposed biosynthetic pathway, rapidly generates stereochemical complexity, uses no protecting groups, and minimizes redox manipulations

Higher-Order Cyclopropenimine Superbases: Direct Neutral Brønsted Base Catalyzed Michael Reactions with α‑Aryl Esters

The synthesis and characterization of six new classes of higher-order superbases, including five that incorporate cyclopropenimine functionality, has been achieved. We propose a nomenclature that designates these as the CG₂, GC₂, PC₃, PC₁, C₃, and GP₂ classes of superbases. The p<i>K</i>_BH+ values were measured to be between 29.0 and 35.6 in acetonitrile. Linear correlations of ten superbase basicities vs that of their substituents demonstrated the insulating effect of the cyclopropenimine core. The molecular structures of several of these materials were obtained by single-crystal X-ray analysis, revealing interesting aspects of conformational bias and noncovalent organization. The types of superbasic cores and substituents were each reliably shown to affect selectivity for deprotonation over alkylation. Higher-order cyclopropenimine and guanidine superbase stability to hydrolysis was found to correlate to basicity. Finally, a GC₂ base was found to catalyze conjugate additions of α-aryl ester pronucleophiles, representing the first report of a neutral Brønsted base to catalyze such reactions

Cyclopropenone Catalyzed Substitution of Alcohols with Mesylate Ion

The cyclopropenone catalyzed nucleophilic substitution of alcohols by methanesulfonate ion with inversion of configuration is described. This work provides an alternative to the Mitsunobu reaction that avoids the use of azodicarboxylates and generation of hydrazine and phosphine oxide byproducts. This transformation is shown to be compatible with a range of functionality. A cyclopropenone scavenge strategy is demonstrated to aid purification

Spin-Center Shift-Enabled Direct Enantioselective α‑Benzylation of Aldehydes with Alcohols

Nature routinely engages alcohols as leaving groups, as DNA biosynthesis relies on the removal of water from ribonucleoside diphosphates by a radical-mediated “spin-center shift” (SCS) mechanism. Alcohols, however, remain underused as alkylating agents in synthetic chemistry due to their low reactivity in two-electron pathways. We report herein an enantioselective α-benzylation of aldehydes using alcohols as alkylating agents based on the mechanistic principle of spin-center shift. This strategy harnesses the dual activation modes of photoredox and organocatalysis, engaging the alcohol by SCS and capturing the resulting benzylic radical with a catalytically generated enamine. Mechanistic studies provide evidence for SCS as a key elementary step, identify the origins of competing reactions, and enable improvements in chemoselectivity by rational photocatalyst design

Complexity-Generating Transformations Enabled by Intramolecular Radical Migration: Alkyl–Arylation of Simple Olefins

A free-radical cascade approach has enabled the develop-ment of a synthetically versatile alkyl–arylation of olefins. This transformation engages an excellent range of olefins, from mono- to tetrasubstituted, without requiring directing or electronically activating groups. Further synthetic advantages, such as the facile generation of quaternary cen-ters and the introduction of heteroaryl groups with Lewis basic nitrogen atoms, also complement transition-metal-catalyzed alkyl–arylation. Vicinal stereoarrays were gener-ated with high levels of diastereoselectivity. The synthetic potential of this transformation was demonstrated by serving as the key step in a concise synthesis of oliceridine, a new painkiller that received FDA approval in 2020