Abstract
Prior research suggests that the Weiss-Cook reaction is a versatile method that can be reliably used to synthesize many complex bicyclic 2:1 condensation products. However, our findings indicate that this reaction often yields unexpected and uncommon products. To better understand these systems' stereochemical and regiochemical characteristics and identify the limitations of the Weiss-Cook reaction, we subjected all isolated substrates to X-ray crystallographic analysis. In synthesizing annelated semibullvalenes and barbaralanes, the bromination-dehydrobromination (Br2 followed by Et3N) of intermediate Weiss-Cook products is crucial. New methods were explored when this step failed for a novel target system. Our previous work, which involved developing a mild electrophilic monobromination protocol for reactive aromatic compounds, enabled the successful bromination-dehydrobromination of an array of bisenol precursors (Weiss-Cook products) to the bridged homotropilidenes of interest using N-bromosuccinimide. This novel method produced high yields of the required bromination-dehydrobromination products when applied to various bisenols, which by previous techniques failed to give the desired products.The mechanism of carboxylic acid anhydride formation involves the condensation of two carboxylic acid moieties via a mixed anhydride intermediate or through the use of dehydrating/acylating agents. However, strained semibullvalene bisanhydrides are unusual in their formation. The bis mixed anhydride is hydrolyzed with water to facilitate a slow cyclization process to produce the desired cyclic anhydride. This water-mediated cyclic anhydride formation pathway may seem counterintuitive, but several examples demonstrate its necessity in producing the desired materials for studying homoaromaticity in the condensed phases. Symmetric and asymmetric semibullvalenes with two side anhydride ring annelations and a top-annelation to a 6-membered ring, were synthesized and studied. However, Dynamic Nuclear Magnetic Resonance Spectroscopy revealed that the 6-annelated systems were fast-equilibrating and not homoaromatic. Despite significant efforts to develop a more strained and potentially homoaromatic 5-annelated system, progress has been impeded by this semibullvalene's high sensitivity to oxygen. Nevertheless, several steps have been developed to guide future work.
The onset of the COVID-19 pandemic severely impeded student access to essential university services to enhance engagement and academic success. Additionally, access to the lab was limited as a measure to curb the spread of the virus. As a result, efforts were focused on devising virtual solutions to aid students with their learning goals. By reorganizing staff responsibilities, creating online sessions, staying closely connected with teaching faculty, and prioritizing student outreach, the number of students utilizing the tutoring program increased from 6% before the pandemic to 53% in a virtual environment. Grade data was also followed to see the academic outcomes of these students to evaluate program success. A research paper resulted from this work.