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Study of the Structure and Photochemical Decomposition of Azidoadamantanes Entrapped in α‐ and β‐Cyclodextrin
Author(s) -
Brinker Udo H.,
Walla Peter,
Krois Daniel,
Arion Vladimir B.
Publication year - 2011
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201001525
Subject(s) - chemistry , azide , alkyl , supramolecular chemistry , cyclodextrin , crystallography , circular dichroism , yield (engineering) , stereochemistry , photodissociation , crystal structure , photochemistry , organic chemistry , materials science , metallurgy
Photolysis of 1‐azidoadamantane ( 1 ), either in its neat state or in alkane solution, yields the dimeric product 4 . In contrast, amino alcohol 3 is formed as the sole product in high yield when 1 is confined within cyclodextrins (CyDs). To understand the discrepancy in product distribution caused by supramolecular encapsulation, CyD inclusion complexes (ICs) of azidoadamantanes were fully characterized. Indeed, intermolecular selectivity was influenced by reactant orientation and mobility. Both, 1‐ ( 1 ) and 2‐azidoadamantane ( 5 ) yield 1:1 ICs with β‐CyD and 1:2 ICs with α‐CyD. As inferred from 2‐D ROESY spectra in D 2 O, 1 is accommodated at the wider rim of β‐CyD with the azido group pointing into the cavity. However, two principal orientations of 5 inside the cavity of β‐CyD were found. Single crystal X‐ray analysis of solid 5 also demonstrates a bimodal orientation within β‐CyD. In addition, the first induced circular dichroism (ICD) study of an alkyl azide entrapped within CyD cavities is reported. From these data, it was concluded that azide 1 is bound more strongly within β‐CyD in H 2 O/EtOH = 8:2 at 293 K ( K a = 20240 ± 1000 M –1 ) than is 2‐azidoadamantane ( 5 ) ( K a = 7450 ± 400 M –1 ).