Direct and sensitized excitation of 3-(N-phthalimido)adamantane-1-carboxylic acid (1) leads to the population of the triplet state that, in the presence of a base, decarboxylates, giving N-(1-adamantyl)phthalimide (2) cleanly and efficiently (Φ = 0.11). The radical initially formed by decarboxylation adds regiospecifically to electron deficient alkenes, whereas radical addition was not observed for electron rich alkenes. The radical addition can also be applied to molecules not bearing adamantanes wherein the electron donor (carboxylate) and the acceptor (phthalimide) are separated by a rigid spacer. The photodecarboxylation induced radical addition of phthalimide derivative 1 to alkenes takes place in good to excellent yields and represents a mild and efficient method for C-C bond formation.

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Phthalimides 1-6 undergo photochemical reactions upon direct irradiation as well as triplet sensitization and give rise to new products. Besides formation of the primary photoproducts, the first photochemical step initiates a subsequent thermal domino reaction or a domino sequence of a thermal and a photochemical reaction. The latter, involving two photochemical intramolecular gamma-H abstractions, was observed with phthalimides 1, 3, and 6 and delivered stereospecifically the hexacyclic benzazepine products 12, 19, and 27, respectively. The lowest triplet states of 1-6 were characterized in several solvents upon direct and acetone-sensitized excitation. The intermolecular electron transfer from triethylamine and DABCO was studied, and the radical anions were observed. Electrochemical measurements showed that intramolecular electron transfer from the adamantyl group of 1-6 to the lowest triplet state of the phthalimides is not feasible. The formation of products can be explained by intramolecular H-abstraction from the (alkyl)adamantane to the excited phthalimide, either from the excited singlet state or a hidden upper excited triplet state.

A series of (1‐adamantyl)phthalimides, 1–4, and (2‐adamantyl)phthalimides, 5–8, characterized by different chain length between the adamantyl and the phthalimide moiety were synthesized, as well as 1‐ and 2‐adamantylphthalimides substituted by nitro 9, 10, and amino group 11, 12, and phthalimides bearing homoadamantyl 13 and protoadamantyl substituent 14 and 15. The compounds were tested for antiproliferative activity in vitro on a series of five human cancer lines: MCF‐7 (breast carcinoma), SW 620 (colon carcinoma), HCT 116 (colon carcinoma), MOLT‐4 (acute lymphoblastic leukemia), H 460 (lung carcinoma), and a non‐tumor cell line HaCaT (human keratinocytes). All compounds except nitro derivatives 9 and 10 exhibited antiproliferative activity. The activity was generally better in the 2‐adamantyl series 5–8 and in the compounds having the longest alkyl spacers as in 4 and 8, or with an amino group as in 9 and 10. The most active compounds with the propylene spacer 4 and 8 showed the highest selectivity toward tumor cells. The activity was found to be due to a delay in the progress through the cell cycle at G1/S phase.