Efficient method for propargylation of aldehydes promoted by allenylboron compounds under microwave irradiation

Highly Regioselective Propargylation/Allenylation of Organolanthanum Reagents with Aldehydes

The metal-mediated propargylation or allenylation of carbonyl compounds is well-adapted to the preparation of homopropargylic or allenylic alcohols, which are multifunctional intermediates in synthetic chemistry. However, the regioselectivity of reactions using propargyl or allenyl metal reagents is difficult to control, owing to the equilibrium between the two species. In our study, propargyl or allenyl organolanthanum reagents were prepared using trimethylsilylpropyne or prop-1-yn-1-ylbenzene substrates. The treatment of the organolanthanum reagents with aldehydes yielded the regioselective products, respectively. This study provides a better understanding of structural specificity and the special chemoselectivity of rare earth metal reagents.

Recent Advances in the Synthesis of Propargyl Derivatives, and Their Application as Synthetic Intermediates and Building Blocks

The propargyl group is a highly versatile moiety whose introduction into small-molecule building blocks opens up new synthetic pathways for further elaboration. The last decade has witnessed remarkable progress in both the synthesis of propargylation agents and their application in the synthesis and functionalization of more elaborate/complex building blocks and intermediates. The goal of this review is to highlight these exciting advances and to underscore their impact.

Allenylboronic Acid Pinacol Ester: A Selective Partner for [4 + 2] Cycloadditions

We have studied the reaction of allenylboronic acid pinacol ester with cyclopentadiene with experimental and computational methods. The reaction occurred efficiently with complete Diels-Alder periselectivity and regioselectivity at the proximal double bond. The concerted mechanism for the observed transformation was computed to be favored over competitive addition to the distal double bond, [3,3]-sigmatropic rearrangements, and stepwise radical mechanism. This unprecedented Diels-Alder reaction enables the construction of synthetically versatile boron-substituted cycloadducts.