Alkaloid−Fullerene Systems through Photocycloaddition Reactions¹

Abstract

The photocycloaddition of tertiary amines to ¿60fullerene (C(60)) is an interesting and useful reaction. We wished to extend the applications of this type of reaction through an investigation of the photoaddition of alkaloids to C(60) for the purpose of synthesizing novel and complex photoadducts that are difficult to obtain by usual methods. Irradiation of tazettine (2) or gramine (3) with C(60) in toluene leads to formation of one monoadduct (6 or 7), whereas scandine (1a) or 10-hydroxyscandine (1b) reacts with C(60) photochemically to give two products, the expected ¿6,6 monoadduct (5a, 5b) and a new type of monoadduct with a bis-¿6, 6 closed structure (4a, 4b). These new structures were characterized by UV-vis, FT-IR, (1)H NMR, (13)C NMR, (1)H-(1)H COSY, ROESY, HMQC (heteronuclear multiple-quantum coherence), and HMBC (heteronuclear multiple-bond connectivity) spectroscopy. The techniques of time-of-flight secondary ion MS (TOF-SIMS) and field desorption MS (FD-MS) were used for the mass determination. (3)He NMR analysis of the product mixture from photoaddition of 1a to C(60) containing a (3)He atom ((3)He@C(60)) led to two peaks at -9.091 and -11.090 ppm relative to gaseous (3)He, consistent with formation of a ¿6, 6-closed monoadduct and a bis-¿6,6 closed adduct. Presumably, the bis-¿6, 6 closed adducts are formed by an intramolecular ¿2 + 2 cycloaddition of the vinyl group to the adjacent 6,6-ring junction of C(60) after the initial photocycloaddition.

Photochemical Reactions as Key Steps in Organic Synthesis

“…For properties of this fullerene, see refs and . In a recent example, the alkaloid scandine is added to C 60 (Scheme ) . After excitation of the fullerene, electron transfer occurs from the alkaloid and a radical ion pair LIX and C 60 •- is generated.…”

Structural Aspects of Fullerene ChemistryA Journey through Fullerene Chirality

“…The sequence includes a photoinduced addition of the tertiary amine subunit of the alkaloid and a [2 + 2] cycloaddition of the pendant vinyl group to the adjacent formal double bond of the fullerene. A second major product (1,2-mono-adduct of C 60 with a regioisomeric substitution pattern on the amine moiety) was also isolated and characterized in the course of a more detailed investigation on the formation of fullerene-fused pyrrolidines by photoinduced cycloaddition between C 60 and the tertiary amine substructures of a selection of alkaloids 27 Diastereoselective Tandem Addition of the Alkaloid Scandine to C 60 750,751 …”

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“…172 The photocycloaddition of tertiary amines with [60]fullerene has been extended to include the formation of alkaloid systems; two single bonds to the fullerene were formed from the carbon atoms adjacent to a tertiary nitrogen atom in the alkaloid. 173 Some secondary amines, such as 1-methylpiperazine, undergo multiple addition to [60]fullerene under photochemical aerobic conditions producing C s symmetrical tetra(amino)fullerene epoxides in excellent yield. 174 The addition of organocopper reagents to [60]fullerene has been extended and produces pentaaryl-monohydro [60]fullerene derivatives with addition patterns identical to the those of the foregoing amino tetra(amino)fullerene epoxides.…”