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UID:69dbb000e65af
DTSTAMP:20260412T104520
DTSTART:20170510T110000
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TRANSP:OPAQUE
DTEND:20170510T110000
URL:https://murmitoyen.com/events/vanille/udem/detail/740760-single-electro
 n-processes-to-enable-c-c-bond-formation
LOCATION:Pavillon Roger-Gaudry \, 2900\, boul. Édouard-Montpetit\, Local M
 -415\, Montréal\, QC\, Canada
SUMMARY:Single Electron Processes to Enable C-C Bond Formation
DESCRIPTION:Conférence PARAZA PHARMA avec le professeur Gary Molander
\nCe
 tte conférence sera prononcée (en anglais) par le professeur Gary Mol
 ander du département de chimie de l'Université de Pennsylvanie.
\nRésu
 mé :In traditional cross-coupling reactions\, a three-step catalytic cycl
 e mechanistically based on 2-electron processes is employed: oxidative add
 ition of a halide at Pdº or Niº\, transmetalation of an organometallic n
 ucleophile with the oxidative addition intermediate\, and reductive elimin
 ation\, which releases the coupled product and regenerates the Pd0 or Niº
  catalyst. Although such methods are highly effective for Csp2-Csp2 coupli
 ng\, extension to 2º and 3º Csp3-hybridized organoboron reagents in part
 icular has proven challenging owing primarily to lower rates of transmetal
 ation\, which is rate limiting in many alkylmetallic cross-coupling protoc
 ols operating under the traditional mechanistic manifold. To date\, strate
 gies aimed at facilitating the transmetalation of Csp3 cross-coupling reac
 tions with functional group-tolerant organoboron or organosilicon reagents
  employ harsh reaction.
\nThe limitations of the transmetalation in cross-
 coupling reactions are inherent to the mechanism of this process at the mo
 st fundamental level\, and thus predispose many Csp3-hybridized alkylmetal
 lic reagents for failure. Described is a novel\, single electron mechanist
 ic paradigm for cross-coupling that avoids this problem. Thus\, dual catal
 ytic cycles are established: a photoredox catalytic cycle\, generating rad
 icals from appropriate precursors\, and a cross-coupling catalytic cycle t
 hat funnels these radicals into a base metal catalytic cycle that effects 
 the cross-coupling. The nature of the cross-coupling cycle\, in which high
 -energy radical intermediates engage the cross-coupling catalyst\, insures
  a cascade of low energy events leading to product\, avoiding the high ene
 rgy of activation associated with previous cross-coupling protocols. Descr
 ibed will be our efforts to develop a suite of radical precursors for cros
 s-coupling\, emphasizing the tolerability of the developed conditions to a
 n unprecedented array of functional groups. The value of generating radica
 ls in a process that is synchronized and catalytic will be emphasized\, bo
 th in dual catalyzed processes and in processes where a subsequent catalyt
 ic transformation is not utilized.
\nHôte : Professeur Shawn Collins
\nI
 nformation supplémentaireBrochure de la conférence
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