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Reliable synthetic routes to isotopically labelled dimethyl [¹³C,²H]diallylmalonates (1) have been developed. Dimethyl diallylmalonates readily undergo transition-metal catalysed cycloisomerisation and the isotopically labelled substrates are expected to be of general utility in the study of the mechanism of such reactions. In the synthetic routes developed, the ²H labelled allyl chains were introduced by reduction of propargyl functionality with Schwartz reagent. The regio- and stereo-selectivity of such reactions allowing highly selective labelling strategies. The ¹³C labelled allyl chains were introduced via Pd-catalysed allylic alkylation of ¹³C- or ²H-labelled dimethyl allylmalonate anions using [3-¹³C1]allyl benzoate as the allylic electrophile. Using these methods, dimethyl [1,7-(E,E)-²H2]hept-1,6-dienyl-4,4-dicarboxylate (5), dimethyl [2,6-²H2]hept-1,6-dienyl-4,4-dicarboxylate (6), dimethyl [1,7-(Z,Z)-²H2]hept-1,6-dienyl-4,4-dicarboxylate (7), dimethyl [1,1,2,6,7,7-²H6]hept-1,6-dienyl-4,4-dicarboxylate (8), dimethyl [1,3-¹³C1,5,7-¹³C1]hept-1,6-dienyl-4,4-dicarboxylate (9), dimethyl [1,3-¹³C1,6-²H1]hept-1,6-dienyl-4,4-dicarboxylate (10), and dimethyl [1,3-¹³C1,7-(E)-²H1]hept-1,6-dienyl-4,4-dicarboxylate (11) have been prepared.

1,8-Bis(N-benzyl-N-methylamino)naphthalene (2) and its hydrogen iodide salt [2H]⁺[I]^– were synthesised from 1,8-diaminonaphthalene. The thermodynamic diastereomer ratios of (2) and [2H]⁺ in [D7]DMF are 73.4:26.6 and 89.7:10.3 respectively at 293 K. The solid state structures of the major dl-(RNRNSNSN) diastereomers were determined by single crystal X-ray diffraction. The minor diastereomers were shown to be the meso-(RNSN) forms by performing ¹H-NMR NOE studies on isotopically desymmetrized 1-(N-benzyl-N-[¹³C]-methylamino)-8-(N'-benzyl-N'-methylamino)naphthalene [¹³C]-2 and the salt [¹³C]-[2H]⁺. In [D7]DMF at 298 K, the meso form of the free base 2 is 0.6 (± 0.07) kcal·mol^–1 less stable than the dl form (ΔH° = –0.64 (±0.03) kcal·mol^–1; ΔS° = –0.18 (±0.13) cal·K^–1mol^–1) and the activation barriers for interconversion are ca. 14.2 (±0.4) and 14.8 (±0.4) kcal·mol^–1 respectively. The effect of solvent polarity on the entropy and enthalpy change on approach to the transition state was studied. An approximate correlation with the solvent dielectric constant was found for both ΔH^# and ΔS^# and this may be ascribed to the development of a net dipole in the transition state due to substantially different hybridisation and geometry at the two nitrogen centres.