Efficient Silver-Mediated Acetalation
of β,β′-Functionalized Chlorins
作者:Jeffrey Zaleski、Tillmann Köpke、Maren Pink
DOI:10.1055/s-2008-1078505
日期:——
We present a novel synthetic strategy to 2,2-dialkoxy-3-oxochlorins [M = 2H, Ni(II), Cu(II)] (i.e., acetaloxochlorins). Reaction of the corresponding 2,3-dioxochlorin with stoichiometric amounts of silver triflate (AgOTf) in the presence of excess alcohol yields the desired acetaloxochlorins within several hours of reflux in up to 90% yield for n-alcohols, and in 25-89% yields for functionalized alcohol substrates. Similar reaction conditions applied to 2-diazo-3-oxochlorins generates the 2,2-dialkoxy-3-oxochlorins (12-60% yields) accompanied by alkoxyporphyrins (10-27% yields). Electronic spectroscopy reveals for the acetaloxochlorins characteristic Ï-Ï* absorption features throughout the visible region and their X-ray crystal structures exhibit marked distortion from planarity of the Ï-conjugated macrocycle due in part to the steric bulk at the periphery.
Expansion by Contraction: Diversifying the Photochemical Reactivity Scope of Diazo-oxochlorins toward Development of <i>in Situ</i> Alkylating Agents
作者:Tillmann Köpke、Maren Pink、Jeffrey M. Zaleski
DOI:10.1021/ja800094e
日期:2008.11.26
diazo-oxochlorins, these products compete with intramolecular exocyclic ring formation by meso-phenyl ring addition, which occurs in up to 76% yield in the absence of substrate. The dependence of product distribution on substrate is established by photolysis in neat dichlorometane. Under these conditions, formation of the Wolff-rearranged product is inhibited and the phenyl addition product dominates (76%) due to
A Facile Synthesis of 2-Diazo-3-oxochlorins by Lewis Acid Activation: Selective Modification of π-Electron Conjugated Macrocycles
作者:Jeffrey Zaleski、Tillmann Köpke、Maren Pink
DOI:10.1055/s-2006-949613
日期:2006.9
We report a new and direct synthesis of 2-diazo-3-oxochlorins [M = 2 H, Ni(II), Cu(ll), Zn(II)]. Reaction of the corresponding 2,3-dioxochlorin with p-toluenesulfonylhydrazine yields the desired 2-diazo-3-oxochlorins in 59-74% yield after a reaction time of three to nine hours. Addition of a stoichiometric amount of Zn(II) acetate leads to coordination of the dione and increases the electrophilicity