Comparison of Pediatric Acute Appendicitis Before and During the COVID-19 Pandemic in New York City.

Acute appendicitis (AA) is the most common abdominal surgical emergency in children and adolescents. In the year immediately following the declaration of the coronavirus disease 2019 (COVID-19) pandemic by the World Health Organization (WHO), there was a precipitous decline in emergency department (ED) visits especially for surgical conditions and infectious diseases. Fear of exposure to severe acute respiratory coronavirus 2 infection resulted in delay in presentation and time to surgery, and a shift toward more conservative management.

Palladium-catalyzed decarboxylative allylic alkylation of diastereomeric β-ketoesters.

The palladium-catalyzed decarboxylative allylic alkylation of diastereomeric β-ketoesters derived from 4--butylcyclohexanone is described. These experiments were performed to elucidate our understanding of stereoablative enantioconvergent catalysis. A detailed analysis of the product distribution, including stereochemical outcome of the products, is included.

The reaction mechanism of the enantioselective Tsuji allylation: inner-sphere and outer-sphere pathways, internal rearrangements, and asymmetric C-C bond formation.

We use first principles quantum mechanics (density functional theory) to report a detailed reaction mechanism of the asymmetric Tsuji allylation involving prochiral nucleophiles and nonprochiral allyl fragments, which is consistent with experimental findings. The observed enantioselectivity is best explained with an inner-sphere mechanism involving the formation of a 5-coordinate Pd species that undergoes a ligand rearrangement, which is selective with regard to the prochiral faces of the intermediate enolate. Subsequent reductive elimination generates the product and a Pd(0) complex.

Heterocycle Formation Palladium-Catalyzed C-H Functionalization.

Heterocyclic compounds are ubiquitous in natural products, pharmaceuticals, and agrochemicals. Therefore, the design of novel protocols to construct heterocycles more efficiently is a major area of focus in the organic chemistry. In the past several years, cyclization reactions based upon palladium-catalyzed C-H activation have received substantial attention due to their capacity for expediting heterocycle synthesis.

Enantioselective decarboxylative alkylation reactions: catalyst development, substrate scope, and mechanistic studies.

α-Quaternary ketones are accessed through novel enantioselective alkylations of allyl and propargyl electrophiles by unstabilized prochiral enolate nucleophiles in the presence of palladium complexes with various phosphinooxazoline (PHOX) ligands. Excellent yields and high enantiomeric excesses are obtained from three classes of enolate precursor: enol carbonates, enol silanes, and racemic β-ketoesters. Each of these substrate classes functions with nearly identical efficiency in terms of yield and enantioselectivity.

Pd-catalyzed intermolecular C-H amination with alkylamines.

C-H amination of N-aryl benzamides with O-benzoyl hydroxylamines has been achieved with either Pd(II) or Pd(0) catalysts. Furthermore, we demonstrate that secondary amines can be directly used with benzoyl peroxide in a one-pot procedure that proceeds via the in situ generation of the appropriate O-benzoyl hydroxylamines. This catalytic reaction provides a new disconnection for the convergent synthesis of tertiary and secondary arylalkyl amines starting from benzoic acids.

Efforts toward rapid construction of the cortistatin A carbocyclic core via enyne-ene metathesis.

Our efforts toward the construction of the carbocylic core of cortistatin A via an enyne-ene metathesis are disclosed. Interestingly, an attempted S(N)2 inversion of a secondary mesylate in our five-membered D-ring piece gave a product with retention of stereochemistry.

Palladium-catalyzed coupling of pyrazole triflates with arylboronic acids.

[reaction: see text] A general protocol for the palladium-mediated Suzuki coupling reaction of pyrazole triflates and aryl boronic acids has been developed. The use of additional dppf ligand was determined to increase product yields allowing for the use of a broad range of reaction substrates.