Synthesis and Use of Bicyclo[1.1.1]pentylaldehyde Building Blocks.

The bicyclo[1.1.1]pentane (BCP) motif is an emerging scaffold in medicinal chemistry because of its bioisosterism to 1,4-phenylene and 1,2-alkynyl functions. The current drawback of its use is the lack of stable versatile synthetic building blocks. Aldehydes are among the most useful functionalities in organic chemistry. In this paper, a simple one-pot procedure from aryl-halides and [1.1.1]propellane is described. Preparation of various BCP molecules is conducted to showcase the versatility of these stable intermediates.

Catalytic Activation of Trimethylsilylacetylenes: A One-Pot Route to Unsymmetrical Acetylenes and Heterocycles.

For the synthesis of unsymmetrical acetylenes, a Sonogashira coupling-deprotection-Sonogashira coupling reaction sequence is often used. Removal of protecting groups requires harsh conditions or an excess of difficult to handle and expensive reagents. Herein, we disclose a novel catalytic method for the selective deprotection of trimethylsilylacetylenes in Sonogashira reaction. The reagent hexafluorosilicic acid, an inexpensive nontoxic compound, was used to promote the selective desilylation. This method enables the efficient synthesis of unsymmetric acetylenes with other silylated functional groups present. Further possibilities of the method were explored by synthesis of heterocycles.

Copper-Catalyzed Ring Opening of [1.1.1]Propellane with Alkynes: Synthesis of Exocyclic Allenic Cyclobutanes.

Despite the long history and interesting properties of propellanes, these compounds still have tremendous potential to be exploited in synthetic organic chemistry. Herein we disclose an experimentally simple procedure to achieve cyclobutane-containing allenes and alkynes through a copper-catalyzed ring opening of [1.1.1]propellane and subsequent reaction with ethynes.