Oxidative Functionalization of Adamantane and Some of Its Derivatives in Solution

Abstract

1,2,4,5-Benzenetetracarbonitrile (TCB) is irradiated in the presence of adamantane (1) and some of its derivatives. The singlet excited state of TCB is a strong oxidant, and there is various evidence, including time-resolved spectroscopy, to prove that SET from the alkane to TCB1* takes place and yields the corresponding radical ions. The adamantane radical cation deprotonates from the bridgehead position, and the resulting radical couples with TCB-•. Deprotonation via the radical cation occurs with a number of substituted adamantanes and remains the exclusive or predominating reaction also with derivatives containing a potential electrofugal group, such as one of the following carbocations: t-Bu, CH2OMe, CH2OH (notable here is that C−H deprotonation is more efficient than O−H deprotonation). A carboxy group is lost more efficiently than a proton, however. In contrast, detaching of such cations is the main process when the radical cations of substituted adamantanes is produced anodically. This different behavior is explained on the basis of thermochemical calculation and of the different environments experienced by the radical cation in the two cases, viz reaction from the solvated radical cation in the first case and from the substrate adsorbed on the anode in the latter one. 1-Methoxyadamantane deprotonates from the methyl group, a reaction explained by the different structure of the radical cation. On the other hand, the radical NO3 •, conveniently produced by photolysis of cerium(IV) ammonium nitrate, reacts by hydrogen abstraction with selective attack at the bridgehead position and little interference by substituents and thus offers a useful way for the selective oxidative functionalization of adamantanes.

Hydrocarbon Activation with Cerium(IV) Ammonium Nitrate: Free Radical versus Oxidative Pathways

“…[32] The acetamino derivatives 21Ϫ23 can only be produced from cage carbocations; these form by further oxidation of the intermediate radicals by CAN, as shown previously for the 1-adamantyl radical. [12] …”

Study on resist performance of chemically amplified molecular resists based on cyclic oligomers

“…26 Especially, it has been reported that the acid yield of polyhydroxystyrene (PHS) protected by AD gradually increases with increasing protection ratio of hydroxyl groups 27 and that the radical cation of adamantane has comparable acidity to mineral acids. 28 Therefore, a radical cation of AD seems to produce a proton and a radical cation of adamantane. Thus, AD group could lead to the enhancement of acid generation efficiency, namely, resist sensitivity.…”

Functionalized Nanodiamonds Part I. An Experimental Assessment of Diamantane and Computational Predictions for Higher Diamondoids

“…Strong single-electron acceptors, like photoexcited 1,2,4,5-tetracyanobenzene (TCB) [59] are able to oxidize alkanes. [19,33,40] The first step of these reactions involves outersphere electron transfer from the alkane to photoexcited TCB [Eq. (8)], followed by proton loss (in solution) from the alkane radical cation forming an alkyl radical [Eq.…”

“…[17] These are well developed for adamantane and its derivatives, [16,17,32] for which single-electron oxidations are usually the most selective. [33] In contrast to adamantane, higher diamondoids contain several non-equivalent tertiary CÀH bonds: from two in 1 and 6 to six in 3; this makes selective CÀH substitutions rather difficult. It was shown previously that the positional selectivities for the C À H substitutions in cage compounds under ionic conditions correlate to a certain extent (exceptions are rare [34] ) with the stability of the respective carbocations.…”