The use of α-cationic phosphonites derived from TADDOL as ancillary ligands has allowed a highly regio- and enantioselective synthesis of substituted [6]carbohelicenes by sequential Au-catalyzed intramolecular hydroarylation of diynes. Key for these results is the modular structure of these new ligands, and the enhanced reactivity that they impart to Au(I)-centers after coordination.

A series of cationic phosphonites, all sharing a TADDOL skeleton but decorated with different positively charged substituents at phosphorus, were synthesized and tested as chiral ancillary ligands on the Au-catalyzed intramolecular hydroarylation of appropriate diynes toward carbo[6]­helicenes with different substitution patterns. Our studies showed that the Au complexes derived from phosphonites bearing 1,3-dimesityl-1,2,3-triazolium and 1,4-dimesityl-1,2,4-triazolium substituents are the best precatalysts for the desired cyclization in terms of regio- and enantioselectivity of the products obtained. In contrast, all of our attempts to prepare Au complexes from cationic phosphonites derived from CAACs failed, and only ligand decomposition products could be isolated.

The synthesis of unprecedented BINOL‐derived cationic phosphonites is described. Through the use of these phosphanes as ancillary ligands in AuI catalysis, a highly regio‐ and enantioselective assembly of appropriately designed alkynes into 1‐(aryl)benzo[5]carbohelicenes is achieved. The modular synthesis of these ligands and the enhanced reactivity that they impart to AuI‐centers after coordination have been found to be the key features that allow an optimization of the reaction conditions until the desired benzo[5]helicenes are obtained with high yield and enantioselectivity.

The reaction of H2 with [RP-W(CO)5] (R = Ph, Me) above 120 °C leads, first, to the secondary diphosphine complex (RPH-PHR)(W(CO)5)2 and then to the primary phosphine complex (RPH2)(W(CO)5). On the basis of DFT calculations, the mechanism most likely involves the addition of H2 to the P–W bond, followed by the formation of the radical [RPH-W(CO)5]• by homolysis of the W–H bond. In the case of [PhNHP-W(CO)5], the hydrogenolysis takes place at the P–N bond and ultimately produces the secondary diaminophosphine complex ((PhNH)2PH)(W(CO)5).

The synthesis and characterization through NMR and Xray crystallography of a series of N-arylpyridiniophosphines and their corresponding Au(I)-derivatives are reported. Because of their acceptor properties, pyridiniophosphines efficiently enhance the electrophilicity of the Au atom in the complexes they form. In our study, this is translated into higher reactivity of the corresponding Au catalysts, which is demonstrated in two mechanistically differentiated cycloisomerizations. Moreover, the steric protection and probably also the electronic stabilization provided by the N-aryl substituents make the active Auspecies more robust and slow down its rate of decay. This allows for an appreciable reduction of the catalyst loadings.