ISSN:
0894-3230
Keywords:
Organic Chemistry
;
Physical Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
2-Diazopropane, generated by photolysis of 2-methoxy-2,5,5-trimethyl-Δ3-1,3,4-oxadiazoline, was trapped in situ by cycloaddition to norbornene, endo- and exo-5-methylnorbornene, endo- and exo-5-phenylnorbornene, endo- and exo-5-methoxycarbonyl norbornene and endo- and exo-dicyclopentadiene. In all cases, only exo addition was observed. In spite of the exo approach of diazopropane to the norbornene double bond, endo substituents at C-5 and/or C-6 influenced the regiochemistry of addition whereas exo substituents did not. The results are interpreted in terms of a concerted, asynchronous mechanism in which C—C bond formation runs well ahead of N—C bond formation, as predicted from theory. The regiochemical control exercised by apparently remote endo substituents provides a new experimental criterion for asynchrony or synchrony of cycloadditions that are known to be concerted.
Additional Material:
5 Tab.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/poc.610030511
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