title: Atom-transfer cyclization with CuSO4/KBH4: a formal "activators generated by electron transfer" process also applicable to atom-transfer polymerization.
abstract: The 4-exo and 5-exo-trig atom-transfer cyclizations of 1, 8a-e, 9, 12, and 13 can be mediated with as little as 0.05 mol % of Cu(TPMA)SO(4)·5H(2)O in the presence of 2.5 mol % of borohydride salts in 10 min at room temperature in air. This formal "activators generated by electron transfer" (AGET) procedure utilizes a cheap and oxidatively stable copper source (CuSO(4)·5H(2)O) and can be carried out in environmentally benign solvents (EtOH). It is possible to alter the product distribution in the 5-endo radical-polar crossover reactions of 10a,b and 11 by tailoring the amount of borohydride. Cyclization onto alkynes 14 and 15 is also possible in only 20 min. Controlled radical polymerization of styrene, with increased rates over conventional atom-transfer radical polymerization (ATRP), can be carried out in a controlled fashion (Mn, PDI) using either CuBr or CuSO(4)·5H(2)O and Bu(4)NBH(4).
authors.affiliation: Department of Chemistry, University of Warwick, Coventry, West Midlands CV4 7AL, UK. a.j.clark@warwick.ac.uk
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Clark
authors.forename: Alana E C
authors.initials: AE
authors.lastname: Collis
authors.forename: David J
authors.initials: DJ
authors.lastname: Fox
authors.forename: Lauren L
authors.initials: LL
authors.lastname: Halliwell
authors.forename: Natalie
authors.initials: N
authors.lastname: James
authors.forename: Rachel K
authors.initials: RK
authors.lastname: O'Reilly
authors.forename: Hemal
authors.initials: H
authors.lastname: Parekh
authors.forename: Andrew
authors.initials: A
authors.lastname: Ross
authors.forename: Andrew B
authors.initials: AB
authors.lastname: Sellars
authors.forename: Helen
authors.initials: H
authors.lastname: Willcock
authors.forename: Paul
authors.initials: P
authors.lastname: Wilson