Biology Reference
In-Depth Information
7.4
Templated Solid-State Reactivity
To develop a CCF as a template for the [2 + 2] photodimerization, we
hypothesized that 1,3-dihydroxybenzene, or resorcinol (res), could
directstackingofolefinslinedwithpyridylgroups.Morespecifically,
we expected that res could be used to assemble and preorganize
trans
′
-bpe) via O-H···N hydrogen
bonds to give, upon ultraviolet (UV) irradiation,
-1,2-bis(4-pyridyl)ethylene (4,4
rctt
-tetrakis(4-
pyridyl)cyclobutane (4,4
′
-tpcb)(Scheme7.5).
O
H
N
N
H
O
H
N
O
N
H
O
hv
solid
O
H
N
O
H
N
N
H
O
N
H
O
Scheme 7.5
-bpe to undergo a cycloaddition
reaction was based on the earlier studies of Aoyama, Ito, and Feldman.
In 1995, Aoyama reported a co-crystal [15] wherein a bis(resorcinol)
anthracene directed stacking of quinones via hydrogen bonds. The
quinones were stacked at 3.80 Å, which was within the distance
criterionofSchmidtforphotodimerization[7].Moreover,inthesame
year, Ito described forced stacking of cinnamate ions in diammonium
salts[16].Althoughthesolidsafordedproductmixtures,itwas
clearthatforcedstackingofolefinswaspossibleusingasecond
component. Feldman had also described a J-shaped naphthalene
dicarboxylic acid that formed a hydrogen-bonded dimer with two
C=Cbondspreorganizedforaphotodimerization[17].Thedimer
isolatedtheolefinsfromtheefectsoflong-rangecrystalpacking.
Theolefinsreactedinquantitativeyieldandgeneratedasingle
cyclobutaneproduct(Scheme7.6).
The fact that res could direct 4,4
′
O
OH
O
H
O
O
O
hv
solid
OH
O
H
O
H
O
O
O
O
H
HO
HO
O
Scheme 7.6
With the studies of Aoyama, Ito, and Feldman in mind, res was
co-crystallized with 4,4
-bpe. As expected, the components formed
adiscretefour-componentassembly2(res)∙2(4,4
′
′
-bpe) with two
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