Organic Letters
Letter
reactions of oxazole pendants offer access to strained cyclic
imines, i.e. reactive electrophilic moieties, potentially suitable for
postphotochemical transformations via existing multicompo-
nent reactions. Additionally, a new three-component reaction
was developed, which involves in situ generation of 1,4-
dielectrophilic species, α,α′-dibromo amide 12, upon treatment
of the primary photoproducts with bromoacetyl bromide, and
subsequent reaction with dinucleophiles to yield fused (hetero)
lactams of varied ring sizes, further diversifying the resulting
polyheterocyclic cores.
Scheme 4. Photocyclization/Oxidation Sequence in Oxazole-
2-yl Tethered Photoprecursors 9
ASSOCIATED CONTENT
* Supporting Information
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The Supporting Information is available free of charge on the
Experimental details and NMR spectra (PDF)
Crystallographic data for 3c (CIF)
Crystallographic data for 11g (CIF)
Crystallographic data for 15 (CIF)
Scheme 5. In Situ Generation of 1,4-Dibromo Synthon 12
AUTHOR INFORMATION
Corresponding Author
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Notes
The authors declare no competing financial interest.
Synthon 12 is a versatile reactive 1,4-dibromide, which can
be engaged by various dinucleophiles under mild conditions to
append the pyrrolidino-benzodiazacane core of the primary [4
+ 4] photoproducts with an additional heterolactam ring as
large as one that is nine-membered, as in the case of
thiosalicylic acid7 (its X-ray structure is shown), Scheme 6.
To summarize, we have demonstrated that photogenerated
aza-o-xylylenes are capable of intramolecular cycloadditions
with tethered oxazole pendants. Unlike previously reported
reactions with the furan-, thiophene-, or pyrrole-based
unsaturated pendants, which give primary photoproducts
containing reactive nucleophilic double bonds, the photoinduced
ACKNOWLEDGMENTS
Support of this research by the NSF (CHE-1362959) is
gratefully acknowledged.
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REFERENCES
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Scheme 6. Further Diversification of the Primary
Photoproducts via the Reactions of 1,4-Dibromo Synthon 12
with Dinucleophiles; ORTEP Drawing of 15 Is Shown
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(4) Photochemistry of minor diamidoenones 7 will be addressed
elsewhere. In this Letter we will focus on the major photoproduct
possessing a 1,3-diazacane core.
C
Org. Lett. XXXX, XXX, XXX−XXX