title: Factors affecting migration of tertiary alkyl groups in reactions of alkylboronic esters with bromomethyllithium.
abstract: The reactions of bromomethyllithium with tert-alkylboronic esters could be of great potential for the formation of quaternary carbon centers but often give poor yields/conversions. Calculations and experimental evidence show that tert-alkyl groups migrate less effectively than other types of alkyl group in such reactions and that O-migration competes. Furthermore, slow/incomplete capture of the bromomethyl reagent by the boronic ester is a problem in more hindered systems, and an additional competing reaction, possibly Li-Br exchange on the bromomethylborate species, also leads to lower yields of migrated products. Based on this, experimental protocols have been devised in which the competing reactions are largely suppressed, leading to higher conversions to migrated product for several substrates.
authors: School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff, CF10 3AT, UK. elliottmc@cardiff.ac.uk
authors: Mark C
authors: MC
authors: Elliott
authors: Keith
authors: K
authors: Smith
authors: D Heulyn
authors: DH
authors: Jones
authors: Ajaz
authors: A
authors: Hussain
authors: Basil A
authors: BA
authors: Saleh
mesh_terms: D000438:Alcohols / Q000138:chemical synthesis* / Q000737:chemistry; D001897:Boronic Acids / Q000737:chemistry*; D004952:Esters / Q000737:chemistry*; D008094:Lithium / Q000737:chemistry*; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D011789:Quantum Theory
chemical_list: D000438:Alcohols; D001897:Boronic Acids; D004952:Esters; D009942:Organometallic Compounds; D008094:Lithium