Ring Expansion to 1-Bromo-1-alumacyclonona-2,4,6,8-tetraene by Insertion of Two Alkyne Molecules into the AlC Bonds

Isolation and Reactivity of an Antiaromatic s-Block Metal Compound

The concepts of aromaticity and antiaromaticity have a long history, and countless demonstrations of these phenomena have been made with molecules based on elements from the p, d, and f blocks of the periodic table. In contrast, the limited oxidation-state flexibility of the s-block metals has long stood in the way of their participation in sophisticated π-bonding arrangements, and truly antiaromatic systems containing s-block metals are altogether absent or remain poorly defined. Using spectroscopic, structural, and computational techniques, we present herein the synthesis and authentication of a heterocyclic compound containing the alkaline earth metal beryllium that exhibits significant antiaromaticity, and detail its chemical reduction and Lewis-base-coordination chemistry.

Additive-Free Conversion of Internal Alkynes by Phosphanylalumanes: Production of Phosphorus/Aluminum Frustrated Lewis Pairs

Internal and terminal alkynes react with phosphanylalumanes, i. e., P-Al single-bond species, through heating but without any additional additives. The reactions with internal alkynes afforded the corresponding adducts with cis-1,2-form in moderate yields (54-80 %). In addition, alkyne adducts thus obtained function as P/Al-based C₂ -vicinal FLPs, and the FLP addition reactions with benzaldehyde and CO₂ were demonstrated. Furthermore, in the reaction of 2,4,6-trimethylphenyl-substituted alkyne adducts with dimethyl acetylenedicarboxylate, an unexpected C_Ar -C_Me bond cleavage characteristic of this system was demonstrated.