A general Rh(III)-catalyzed synthesis of naphthyridinone derivatives is described. It relies on a double-activation and directing approach leveraging nicotinamide N-oxides as substrates. In general, high yields and selectivities can be achieved using low catalyst loadings and mild conditions (room temperature) in the couplings with alkynes, while alkenes require slightly more elevated temperatures.

A family of arylsilylcarbinols was synthesized and investigated as chiral auxiliaries for oxacarbenium ion reactions. The optically pure arylsilylcarbinols were prepared using Noyori's transfer hydrogenation catalyst 11. The transfer hydrogenation shows very good enantioselectivities and turnover efficiency for the aryl silyl ketones and is the method of choice for preparing these optically pure alcohols. The diastereoselective addition of allyltrimethylsilane to an in situ generated oxacarbenium ion was explored using Marko's conditions. The selectivity for a representative aliphatic aldehyde was very good, but the selectivity was significantly reduced with unsaturated and aromatic aldehydes. The range of selectivities with different auxiliaries was narrow, and the most practical auxiliary is the phenylsilylcarbinol 2.

The origin of the high reactivity and site selectivity of pyridine N-oxide substrates in O-pivaloyl hydroxamic acid-directed Rh(III)-catalyzed (4+2) annulation reactions with alkynes was investigated computationally. The reactions of the analogous pyridine derivatives were previously reported to be slower and to display poor site selectivity for functionalization of the C(2)-H vs the C(4)-H bonds of the pyridine ring. The N-oxide substrates are found to be more reactive overall because the directing group interacts more strongly with Rh. For N-oxide substrates, alkyne insertion is rate-limiting and selectivity-determining in the reaction with a dialkyl alkyne, but C-H activation can be selectivity-determining with other coupling partners such as terminal alkynes. The rates of reaction with a dialkyl alkyne at the two sites of a pyridine substrate are limited by two different steps: C-H activation is limiting for C(2)-functionalization, while alkyne insertion is limiting for C(4)-functionalization. Consistent with the observed poor site selectivity in the reaction of a pyridine substrate, the overall energy barriers for functionalization of the two positions are nearly identical. High C(2)-selectivity in the C-H activation step of the reaction of the N-oxide is due to a cooperative effect of the C-H Brønsted acidity, the strength of the forming C-Rh bond, and intramolecular electrostatic interactions between the [Rh]Cp* and the heteroaryl moieties. On the other hand, some of these forces are in opposition in the case of the pyridine substrate, and C(4)-H activation is moderately favored overall. The alkyne insertion step is favored at C(2) over C(4) for both substrates, and this preference is largely influenced by electrostatic interactions between the alkyne and the heteroarene. Experimental results that support these calculations, including kinetic isotope effect studies, H/D exchange studies, and results using a substituted pyridine, are also described.

An advanced intermediate for the synthesis of amphidinol 3 has been prepared. A cross-metathesis reaction was used to couple the C1-C12 and C13-C26 segments. An unusual beta-alkoxy alkyllithium reagent was generated from this segment and added to a Weinreb amide to assemble the C1-C52 section of amphidinol 3. These compounds represent some of the most advanced intermediates reported to date for the synthesis of amphidinol 3.

The development of a synthetic route to manufacture the drug candidate AMG 925 on kilogram scale is reported herein. The hydrochloride salt of AMG 925 was prepared in 23% overall yield over eight steps from commercially available raw materials, and more than 8 kg of the target molecule were delivered. The synthetic route features a Buchwald−Hartwig amination using BrettPhos as ligand and conducted to afford 12 kg of product in a single batch. In addition, this work highlights the challenges associated with the use of poorly soluble process intermediates in the manufacture of active pharmaceutical ingredients. Creative solutions had to be devised to conduct seemingly routine activities such as salt removal, pH adjustment, and heavy metal scavenging due to the low solubility of the process intermediates. Finally, a slurry-to-slurry amidation protocol was optimized to allow for successful scale-up.