SET-promoted photoaddition reactions of N-α-trimethylsilylmethyl-N,N-dibenzylamines with fullerene C60. Electronic factors that govern photoaddition efficiencies

Single Electron Transfer-Promoted Photochemical Reactions of Secondary N-Trimethylsilylmethyl-N-benzylamines Leading to Aminomethylation of Fullerene C60

“…The final observation made in the investigation described above that is worthy of brief discussion is the formation unsymmetric fulleropyrolidines in photoreactions of specific secondary amines with C 60 . In a manner that is similar to observations made in our earlier studies, these adducts are produced as major products in photoreactions of only N -trimethylsilylmethyl- N -benzylamines containing electron-withdrawing substituents on the phenyl ring. Following earlier proposals made by Foote and Baciocchi, we suggested that cycloadducts of this type are produced in photoreactions of amines and C 60 through a route involving the intermediacy of singlet oxygen produced by energy transfer from T1 C 60 .…”

“…These efforts have led to methods that enable the synthesis of fullerene derivatives that can be widely employed in the material − and biological − sciences. Among the large variety of synthetic methodologies devised thus far, photoinduced single electron transfer (SET) reactions with electron donors have become attractive for the preparation of substituted fullerenes because they can be carried out under environmentally benign conditions using visible light and they generate unique products. − …”

“…The results of a number of earlier studies demonstrated that aminium radicals, arising by SET oxidation of tertiary amines possessing α-trialkylsilyl substituents, undergo rapid silophile-induced desilylation to generate aminomethyl radicals in a regioselective manner. , Moreover, the presence of α-trialkylsilyl groups in these amines reduces their oxidation potentials , and, consequently, extends the range of electron acceptors that can be utilized in these SET-promoted C–C bond forming processes. These properties have enabled the use of tertiary α-trialkylsilyl-substituted amines in a wide variety of SET-promoted photochemical reactions with saturated , and α,β-unsaturated ketones, , phthalimides, − and fullerene. , …”

Control of Chemoselectivity of SET-Promoted Photoaddition Reactions of Fullerene C60 with α-Trimethylsilyl Group-Containing N-Alkylglycinates Yielding Aminomethyl-1,2-dihydrofullerenes or Fulleropyrrolidines

“…The mechanism of formation of aminomethyl-1,2-dihydrofullerenes seems to follow the pathway suggested earlier by our studies (Scheme ). It is assumed that because the singlet excited state of fullerene ( 1 C 60 *) undergoes rapid and efficient intersystem crossing (Φ ISC = 1) to form the triplet excited state of C 60 ( 3 C 60 *) , and, moreover, the concentrations of the glycinates are in the 2.5 mM range and their oxidation potentials ( E ox < 1 V vs SCE) are lower than the reduction potential of 3 C 60 * ( 3 E red = 1.14 V vs SCE) (see Table S1 in the Supporting Information), it is likely that bimolecular SET from glycinates to 3 C 60 * takes place favorably to form aminium radicals 21 .…”

“…In our studies aimed at exploring applications of amine SET photochemistry to the synthesis of functionalized fullerenes, , we observed that photoreaction of C 60 with α-trimethylsilyl-substituted amines in deoxygenated conditions promotes the formation of aminomethyl-1,2-dihydrofullerenes via exclusive generation and the addition of α-amino radicals produced by sequential SET-desilylation processes from α-trimethylsilyl amines. More recently, we found that both α-trimethylsilyl and α-alkoxycarbonyl group-containing amines 14 (i.e., ethyl N -alkyl- N -((trimethylsilyl)­methyl)­glycinates) serve as precursors of not only α-amino radicals 15 but also azomethine ylides 17 (Scheme ).…”