New methods for organometallic synthesis: Stereoselective ligand construction and transition metal mediated transformations.

摘要

Chemical transformations relying on catalytic amounts of transition metals have been an area of recent interest. To expand the role of organocuprates in organic synthesis and to reduce the cost and environmental concerns associated with waste disposal, alkylation of several electrophiles with functionalized organozinc, reagents using catalytic amounts of organocuprates was investigated. alpha,beta-Unsaturated ketones and allylic epoxides were screened and several were found to be reactive under the coupling conditions.; The occurrence of medicinally valuable natural products containing polyene portions of varying length and stereochemistry has prompted the development of methods to construct these materials in a concise, stereoselective manner. To address these issues, an organometallic approach to the construction of polyenes was performed. The methodology relies on a conjunctive tetraene equivalent and the preservation of double bond geometry in palladium(0) catalyzed couplings of vinyl and aryl halides. Utilizing this methodology, several all ( E) polyenes were constructed.; Given the interest in the structure and aggregation states of organocuprates, an electrospray ionization mass spectrometry (ESMS) study was performed. Several lithiocuprates were subjected to ESMS and mass spectra were obtained. Offering a solution state picture of organocuprates, ESMS suggests that the predominant species in solution is dimeric.; The widespread utility of stereochemically pure binaphthyls for asymmetric synthesis prompted an investigation for the construction of these reagents employing a nonracemic chiral tether to achieve stereoselective biaryl bond formation. Endeavoring to phosphinylate the derived binaphthyls, a new method for the conversion of aryl sulfonates to triarylphosphines was developed. In conjunction with catalytic palladium(0), diphenylphosphine-borane was shown to serve as an effective phosphinylating agent for a variety of naphthyl nonaflates. Amine-boranes were also investigated under these conditions, and were found to serve as hydride donors. Employing dimethylamine-borane and catalytic palladium(0), the facile deoxygenation of aryl sulfonates was demonstrated.