Selective synthesis of C32- and C20-monoiodinated chlorophyll derivatives

I2-mediated coupling of quinazolinone enamines with 2-aminopyridines: a new strategy to access spiroquinazolinones

“…Furthermore, subjecting I and 2-aminopyridine ( 2a ) to the standard conditions led to isolation of product 3p in a yield of 84% (Scheme 2b). On the basis of the control experiment and the related reference, 29 a plausible mechanism for this transformation was derived, as shown in Scheme 2c. According to this mechanism, first iodine-mediated oxidative iodination of quinazolinone enamine 1 generates the iodonium salt intermediate I , and then nucleophilic substitution of iodide I by 2 produces the desired spiroquinazolinone iodide 3 .…”

Alternative synthesis of 3-acetyl, 3-epoxy, and 3-formyl chlorins from a 3-vinyl chlorin, methyl pyropheophorbide-a, via iodination

“…[21][22][23][24][25][26][27][28][29][30][31][32][33] We have studied reaction of 1 with I 2 and phenyliodine(III) bis(trifluoroacetate) (PIFA), and established the conditions for selective iodination at the C3-vinyl group and the C20-position, respectively. 34,35 The C3-vinyl group was iodinated by 1 equiv I 2 and 0.5 equiv PIFA to give the iodinated intermediate (possibly the C3-iodonium form), and 2 equiv I 2 together with 1 equiv PIFA enabled additional iodination at the C20-position. The C3-iodonium was transformed into the iodohydrin by treatment of water, while the iodine atom was removed from the iodonium by NaN 3 .…”

“…36 Similarly, the vinyl group at the C3-position of 1 can also be converted into the C3-[(1-hydroxy-2-iodo)ethyl], C3-[(1-methoxy-2-iodo)ethyl] and C3-[(1-ethoxy-2-iodo)ethyl] groups by the I 2 -PIFA system (Scheme 1). 35 Compound 1 was mixed with I 2 (1.2 equiv) and PIFA (0.52 equiv) in 1,2-dichloroethane, followed by stirring at room temperature for 1 h. Then ethylene glycol was added to this solution, and an additional stirring afforded an ethylene glycol adduct 2, possessing a [1-(2-hydroxyethyloxy)-2-iodo]ethyl moiety at the C3-position, in 50% isolated yield.…”