Concise Synthesis of the Isothiourea Organocatalysts Homobenzotetramisole and Derivatives

A concise approach to the synthesis of homobenzotetramisole and derivatives is described. Our strategy features a one-pot acylation–cyclization of 2-aminobenzothiazole with α,β-unsaturated acid chlorides to afford annulated pyrimidones. Subsequent Grignard addition followed by acid-promoted dehydration and reduction provides good overall yields of the title compounds in three steps and in quantities up to 10 g. The synthesis employs low-cost and readily available starting materials and enables access to both optical antipodes of these increasingly useful nucleophilic catalysts following chiral separation

3‑Alkenyl-2-silyloxyindoles in Vinylogous Mannich Reactions: Synthesis of Aminated Indole-Based Scaffolds and Products

The first Lewis acid catalyzed vinylogous Mukaiyama-type Mannich addition of 3-alkenyl-2-silyloxyindoles to in situ generated <i>N</i>-Boc imines has been established, which affords chiral α-alkylidene-δ-amino-2-oxindole products with good efficiency and complete γ-site- and <i>Z</i>-selectivity. The reaction is wide in scope, as it can be applied with equal convenience to different silyloxyindole donors and aromatic or aliphatic aminal-derived aldimine acceptors. The utility of these scaffolds is demonstrated by their easy transformation into either spirocyclopropane oxindole or homotryptamine-like products, featuring nontraditional indole-based skeleton connections

Enantioselective Synthesis of Cyclobutenes by Intermolecular [2+2] Cycloaddition with Non‑<i>C</i>₂ Symmetric Digold Catalysts

The enantioselective intermolecular gold­(I)-catalyzed [2+2] cycloaddition of terminal alkynes and alkenes has been achieved using non-<i>C</i>₂-chiral Josiphos digold­(I) complexes as catalysts, by the formation of the monocationic complex. This new approach has been applied to the enantioselective total synthesis of rumphellaone A