All-carbon quaternary stereogenic centers in acyclic systems through the creation of several C-C bonds per chemical step.

In the past few decades, it has become clear that asymmetric catalysis is one of the most powerful methods for the construction of carbon-carbon as well as carbon-heteroatom bonds in a stereoselective manner. However, when structural complexity increases (i.e., all-carbon quaternary stereogenic center), the difficulty in reaching the desired adducts through asymmetric catalytic reactions leads to a single carbon-carbon bond-forming event per chemical step between two components. Issues of efficiency and convergence should therefore be addressed to avoid extraneous chemical steps. In this Perspective, we present approaches that tackle the stimulating problem of efficiency while answering interesting synthetic challenges. Ideally, if one could create all-carbon quaternary stereogenic centers via the creation of several new carbon-carbon bonds in an acyclic system and in a single-pot operation from simple precursors, it would certainly open new horizons toward solving the synthetic problems. Even more important for any further design, the presence of polyreactive intermediates in synthesis (bismetalated, carbenoid, and oxenoids species) becomes now an indispensable tool, as it creates consecutively the same number of carbon-carbon bonds as in a multi-step process, but in a single-pot operation.

Multifarenes: new modular cavitands.

Multifarenes, a new class of macrocycles, which are constructed of alternating building blocks, are conveniently accessible by three complementary syntheses that provide modularity and scalability. In addition to metal-ion coordination, these cavitands show increased flexibility with increasing ring size, offering opportunities for induced fit to guest molecules.

Regio- and stereoselective carbometallation reactions of N-alkynylamides and sulfonamides.

The carbocupration reactions of heterosubstituted alkynes allow the regio- and stereoselective formation of vinyl organometallic species. N-Alkynylamides (ynamides) are particularly useful substrates for the highly regioselective carbocupration reaction, as they lead to the stereodefined formation of vinylcopper species geminated to the amide moiety. The latter species are involved in numerous synthetically useful transformations leading to valuable building blocks in organic synthesis. Here we describe in full the results of our studies related to the carbometallation reactions of N-alkynylamides.

A unique approach to aldol products for the creation of all-carbon quaternary stereocentres.

Among the challenges facing asymmetric synthesis the selective construction of quaternary stereogenic centres, particularly those bearing all-carbon substituents, stands out. The aldol reaction has the potential to create such stereocentres, but, despite the many advances in this field, a highly selective and efficient procedure has remained elusive. Here we show that, by choosing an alternative retrosynthetic approach, such products can be prepared in a highly selective fashion. Through the consecutive addition of several organometallic derivatives, an allylzinc reagent is prepared and, on addition to an aldehyde, an aldol-type product is created. The one-pot operation involves the construction of three new carbon-carbon bonds and the formation of an all-carbon quaternary stereocentre. The products of the reaction are amenable to downstream modification, and the procedure should find applications in the fields of natural product synthesis and drug discovery.