derivatives,14 and fullerene due to their potential application in medicinal chemistry, pharmaceuticals and so on. A few years ago, it has been reported that, when in the fullerene derivatives is present a long alkyl chain the fulleropyrrolidine derivatives showed considerable solubility in the organic solvents.15,16 Owing to the difficulty of synthesizing phenols with a long unsaturated chain –like the fifteen carbon atom chain in the meta position- cardanol represents a peculiar, simple and easily available and precious precursor used as starting material for the synthesis of various derivatives. Several functionalizations of cardanol moiety have been obtained by reactions of the aromatic ring, hydroxy group (i.e. alkylation, nitration etc.) as well as the unsaturations on the chain in the meta position.17 These reasons prompted us to synthesize and characterize novel cardanol based fulleropyrrolidines starting from cardanol precursors.
Results and Discussion
Cardanol oil, obtained by vacuum distillation of CNSL, was redistilled twice using a Vigreux column. Three different fractions were separately collected and the second one was used as starting material for the preparation of cardanol precursors for the fulleropyrrolidine derivatives, reported in this work. GC-MS and NMR analyses were carried out in order to determine the composition of the fractions. They confirmed that the mono unsaturated compound, 3-n- pentadeca-8-enylphenol, 1a, was the main component of the second fraction; with small amounts (< 1%) of saturated, di- and tri-olefinic components (respectively, 3-n-pentadecylphenol, 3-n- pentadeca-8,11-dienylphenol, and 3-n-pentadeca-8,11,14-trienylphenol).
Hydrogenated cardanol 1b (3-n-pentadecylphenol) can be easily obtained as pure compound by hydrogenation of the double bond(s), present in the side-chain, of technical grade distilled cardanol and subsequent distillation and/or crystallization. In this way, several functionalizations of the aromatic ring or hydroxy group (i.e. alkylation) can be performed without undesirable side-reactions ascribable to olefinic moiety. Compound 1b, successively underwent to alkylation reactions, gave the compounds 1c, 1d (Scheme 1).18
OHR1CNSLdistillationhydrogenationOHR11a1bOHR11c, 1dalkylationR2R2R2
1a: R1=C15H29 R2=H; 1b: R1=C15H31 R2=H, 1c: R1=C15H31 R2=t-butyl; 1d: R1=C15H31 R2=t-amyl
Scheme 1. Production processes of the cardanol-based precursors (1a-1d) from CNSL.
Compounds 1a-1d were used as starting materials for the preparation of the aldehyde precursors 5a-5e which effectively reacted with C60 to obtain the new fulleropyrrolidines reported in this paper. So that, cardanol derivatives 3a-3d were prepared in almost quantitative
