Homogeneous gold-catalyzed cyclopropanation has emerged as a powerful method in organic synthesis due to its rich chemistry and fascinating reactivity. This thriving strategy is remarkable for its mild conditions, good selectivity, and high efficiency, which provides complementarity and orthogonality to traditional metal-catalyzed cyclopropanation. This review summarizes recent advances in gold-catalyzed cyclopropanation divided by the type of carbenoid precursors. Besides the commonly used diazo compounds, current approaches enable readily available enynes, propargyl esters, cyclopropenes, cycloheptatrienes, alkynes, and sulfonium ylides as safer surrogates in the realm of gold carbenoid chemistry. Meanwhile, these reactions allow for the rapid building of molecular complexity including synthetically useful and intricate cyclic, heterocyclic, and polycyclic skeletons. The combination of the new reactivity of gold complexes with their capability to catalyze cyclopropanations may lead to myriad opportunities for the design of new reactions. Furthermore, the synthetic utilities of such superior methods have also been illustrated by the total syntheses of selected natural and biologically interesting products and the asymmetric formation of challenging target molecules.

Although chiral allene preparation via formal SN2’ nucleophilic substitutions of enantioenriched propargylic derivatives or metal-catalyzed reactions of racemic propargylic derivatives has attracted considerable attention and found applications in many areas of research, direct use of propargylic alcohols instead of propargylic derivatives for catalytic asymmetric allene synthesis is unknown. Here, we show that a highly enantioselective synthesis of tetrasubstituted allenes from racemic propargylic alcohols has been realized by organocatalysis with good efficiency (up to 96% yield and 97% ee). The intermolecular C–C and C–S bond formation was achieved efficiently with simultaneous stereocontrol over the axial chirality. Furthermore, an adjacent quaternary stereocenter could also be constructed. Mechanistically, the reaction may involve efficient stereocontrol on the propargylic cation by its chiral counter anion or 1,8-conjugate addition of para-quinone methides. In sharp contrast to previous central chirality construction, this process employs quinone methides for axial chirality construction.

Ag old(I)-catalyzed … …i ntermolecular annulation of N-allenamides at the proximal C = Cb ond has been achieved. In their Communication on page 14849 ff., J. Zhang et al. show that both enantiomers of the products are obtained with high regio-, diastereo-, and enantioselectivity by using either diastereomer of ac hiral phosphoramidite as ligand. In the picture,t he enantiomers of the products are easily controlled by the magicians hands with the aid of the gold rings on the fingers.