can be exchanged with D,O. Thus, two insertions of two adamantylidenes into two different 0 -H bonds of fl-CD have taken place. The absolute amount of OH insertion products 4 B-CD and 5 . 8-CD detected by FAB mass spectrometry (Scheme 1 ) is not yet known. Since these compounds could not be found by CP/MAS I3C N M R spectroscopy. they must have been formed each in less than 5 YO yield.
Adamantylidene is believed to be a ground-state singlet carbene. and the generation of the triplet state fails even in the presence of photosensitizers.'t51 The question of whether adamantylidene entrapped in ,6-CD is also a singlet cannot be answered a t this time. Laser flash photolysis studies may solve this problem, as well as answer questions concerned with the detailed differences in the reactive behavior of a "free" adamantanylidem and a (partially) entrapped one.
If the carbene 2 . 8-CD cannot easily encounter another reaction partner, it could rearrange to the highly strained adamantene 6, which is known to dimerize[l6I immediately, although it has been shown to exist in a matrix at low temperature." ' 1 This reaction, however, does not appear to take place if adamantylidene 2 is entrapped in B-CD.""
In conclusion, our results strongly suggest that we have established the first intra-and intermolecular carbene insertions within any constrained molecular reaction vessel.
Erperinientol Procedure
I . /i-CD: A solution of 1 (0.49 g, 3 mmol) in diethyl ether ( I 2 mL) was added to a solution of 8-CD hydrate (3.4 g, 3 mmol) in water (150 mL). After the mixture had been stirred for one day. the precipitate was filtered off. washed 9evera1 tiines with water and ether. and then dried in the desiccator. Yield: 2.9 g (2.4 mmol. 81 I!'")