Development of Novel, Regioselective Borylation Protocols

Organoboron compounds are highly valued synthetic intermediates due to their diverse array of reactivity, which is often utilized in the synthesis of valuable organic molecules. For this reason, there is significant interest in the development of novel borylation protocols, especially those whose products are suitable for further synthetic transformations towards valuable classes of compounds. Research in organoboron synthesis has been geared heavily toward transition metal-catalyzed addition to double and triple bonds, though an increasing number of publications detail transition metal-free borylation techniques involving substrate-mediated activation of a diboron reagent. This dissertation describes the author's contributions to the development of both a transition metal-catalyzed diboration and a transition metal-free protoboration. A transition metal-free diboration of alkynamides is described in Chapter 1 which uses the unsymmetrical, differentially protected diboron reagent, pinBBdan. The method installs both boron moieties in a regio- and stereoselective fashion. The products have synthetic value because they are shown to have chemoselectivity in downstream cross-coupling reactions; chemoselectivity is made possible by to the significant difference in Lewis acidity of the pinacol and diaminonapthalene-protected boron centers. This method allows for facile synthesis of tetrasubstituted alkenes with a set geometry about the double bond. A protoboration of allenes employing a Cu(II) catalyst under aqueous and atmospheric conditions is described. Though Cu(I)-catalyzed allene protoboration is well-described in the literature, this is the first report of an analogous Cu(II)-mediated process. The selectivity of the reaction is ligand-controlled, and moderate to good regioselectivities and yields can be achieved through use of a triphenylphosphine as ligand. The method is an environmentally friendly and facile means by which to borylate a challenging cumulated substrate.

Name thesis:degree_name

Ph. D.

Level thesis:degree_level

doctoral

Discipline thesis:degree_discipline

Chemistry

Department dc:contributor.department

Chemistry

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

2018

Author dc:creator

• Snead, Russell Franklin

Chair dc:contributor.committeechair

• Santos, Webster L.

Committee members dc:contributor.committeemember

• Kingston, David G. I.
• Tanko, James M.
• Carlier, Paul R.

• borylation
• transition metal-catalyzed
• transition metal-free
• allenes
• alkynamides

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Dc Identifier Other

vt_gsexam:16959

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/85003