Rhodium-Catalyzed Regio- and Enantioselective Direct Allylation of Methyl Ketones

We report a highly branch-selective and enantioselective allylic alkylation of simple ketones with racemic aliphatic allylic carbonates under mild conditions. By using a Rh–bisoxazolinephosphine system and catalytic amounts of a base in THF, a series of chiral β-branched γ,δ-unsaturated ketones were obtained with excellent regio- and enantioselectivities. An outer-sphere nucleophilic substitution C–C bond-formation process is proposed on the basis of mechanistic studies.

A Consecutive Ring-Expansion Strategy towards the Macrocyclic Core of the Solomonamide Natural Products

A synthetic strategy based on the application of three consecutive ring-expansion reactions has been used in the synthesis of analogues of the macrocyclic core of the solomonamide natural products. Starting from a simple, readily available tetrahydrocarbazole, oxidative ring expansion is followed by two further 3- and 4-atom ring-expansion reactions, enabling the insertion of amino acid and hydroxy acid derived linear fragments into 15- to 17-membered-ring-enlarged macrocyclic products.

London Dispersion Stabilizes Chloro-Substituted cis-Double Bonds

We present a combined experimental and computational study on the thermodynamic stability of cis- and trans-alkenes substituted with dispersion energy donor (DED) groups. To investigate the role of noncovalent interactions on equilibrium of cis- and trans-alkenes we utilized hydrochlorination reactions. While the general assumption is that increasing steric bulk favors the trans-alkene, we observe an equilibrium shift towards the more crowded cis-alkene with increasing substituent size. With the aim to quantify noncovalent interactions, we performed a double mutant cycle to experimentally gauge the attractive potential of bulky substituents. Additionally, we utilized local energy decomposition analysis at the DLPNO-CCSD(T)/def2-TZVP level of theory. We found LD interactions and Pauli exchange repulsion to be the most dominant components to influence cis- and trans-alkene equilibria.