Byron K. Peters

Enantioselective Synthesis of Chiral Sulfones by Ir-Catalyzed Asymmetric Hydrogenation : A Facile Approach to the Preparation of Chiral Allylic and Homoallylic Compounds

A highly efficient and enantioselective Ir-catalyzed hydrogenation of unsaturated sulfones was developed. Chiral cyclic and acyclic sulfones were produced in excellent enantioselectivities (up to 98% ee). Coupled with the Ramberg-Bäcklund rearrangement, this reaction offers a novel route to chiral allylic and homoallylic compounds in excellent enantioselectivities (up to 97% ee) and high yields (up to 94%).

Highly Enantioselective Asymmetric Isomerization of Primary Allylic Alcohols with an Iridium–N,P Complex

Highly Enantioselective Asymmetric Isomerization of Primary Allylic Alcohols with an Iridium-N,P Complex

Chiral Hetero‐ and Carbocyclic Compounds from the Asymmetric Hydrogenation of Cyclic Alkenes

Several types of chiral hetero- and carbocyclic compounds have been synthesized by using the asymmetric hydrogenation of cyclic alkenes. N,P-Ligated iridium catalysts reduced six-membered cyclic alkenes with various substituents and heterofunctionality in good to excellent enantioselectivity, whereas the reduction of five-membered cyclic alkenes was generally less selective, giving modest enantiomeric excesses. The stereoselectivity of the hydrogenation depended more strongly on the substrate structure for the five- rather than the six-membered cyclic alkenes. The major enantiomer formed in the reduction of six-membered alkenes could be predicted from a selectivity model and isomeric alkenes had complementary enantioselectivity, giving opposite optical isomers upon hydrogenation. The utility of the reaction was demonstrated by using it as a key step in the preparation of chiral 1,3-cis-cyclohexane carboxylates.

An Enantioselective Approach to the Preparation of Chiral Sulfones by Ir-Catalyzed Asymmetric Hydrogenation

Several chiral sulfonyl compounds were prepared using the iridium catalyzed asymmetric hydrogenation reaction. Vinylic, allylic and homoallylic sulfone substitutions were investigated, and high enantioselectivity is maintained regardless of the location of the olefin with respect to the sulfone. Impressive stereoselectivity was obtained for dialkyl substitutions, which typically are challenging substrates in the hydrogenation. As expected, the more bulky Z-substrates were hydrogenated slower than the corresponding E isomers, and in slightly lower enantioselectivity.

Enantio- and Regioselective Ir-Catalyzed Hydrogenation of Di- and Trisubstituted Cycloalkenes

A number of cyclic olefins were prepared and evaluated for the asymmetric hydrogenation reaction using novel N,P-ligated iridium imidazole-based catalysts (Crabtree type). The diversity of these cyclic olefins spanned those having little functionality to others bearing strongly coordinating substituents and heterocycles. Excellent enantioselectivities were observed both for substrates having little functionality (up to >99% ee) and for substrates possessing functional groups several carbons away from the olefin. Substrates having functionalities such as carboxyl groups, alcohols, or heterocycles in the vicinity of the C═C bond were hydrogenated in high enantiomeric excess (up to >99% ee). The hydrogenation was also found to be regioselective, and by controlling the reaction conditions, selective hydrogenation of one of two trisubstituted olefins can be achieved. Furthermore, trisubstituted olefins can be selectively hydrogenated in the presence of tetrasubstituted olefins.

Formal Total Synthesis of Aliskiren

The efficient and selective formal total synthesis of aliskiren is described. Aliskiren, a renin inhibitor drug, has received considerable attention, primarily because it is the first of the renin inhibitor drugs to be approved by the FDA. Herein, the formal synthesis of aliskiren by iridium-catalyzed asymmetric hydrogenation of two allylic alcohol fragments is reported. Screening a number of N,P-ligated iridium catalysts yielded two catalysts that gave the highest enantioselectivity in the hydrogenation, which gave the saturated alcohols in 97 and 93 % ee. In only four steps after hydrogenation, the fragments were combined by using the Julia-Kocienski reaction to produce late-stage intermediate in an overall yield of 18 %.

An unexpected re-arrangement of the antibiotic carbapenem core to new 1,4-diazepin-5-one scaffolds

Herein we report a peculiar organocatalyzed domino-reaction on the carbapenem core structure. As previously reported, 30 mol% of proline yields diazabicyclo[4.2.1]nonane analogues, while we currently report the formation of novel 1,4-diazepin-5-ones from the same starting material in the presence of 100 mol% proline. The inherent chirality of the starting material led to the stereochemical preference of the products with excellent diastereoselectivity (>99 : 1). The diazepinone products were confirmed using X-ray diffraction and 2D-NMR structure elucidation. A plausible mechanism of the re-arrangement, involving an unactivated retro-Dieckmann condensation, is also presented.