Phosphine-catalysed cycloaddition of buta-2,3-dienoates and but-2-ynoates to [60]fullerene

Organofullerene Materials

“…Finally, buta-2,3-dienoates and buta-2-ynoates, in the presence of phosphine as catalyst, have been found to react with C 60 in a [3+2] fashion [83,84], contrary to the earlier observations of yielding [2+2] cycloadducts [85]. …”

Fullerenes: functionalisation and prospects for the use of derivatives

“…A series of successive prototropic shifts is followed by b-elimination of phosphine giving rise to fullerenocyclopentene 44. 85,86 The first example of cycloaddition of ylide 45, prepared from N-benzyl-1-(4-nitrophenyl)chloromethylideneamine (46), to C 60 fullerene was reported. 87 However, based on the 13 C and 1 H NMR data, the authors suggest that, in addition to the normal -adduct 47, the reaction yields an approximately equal amount of a [5][6]-adduct with an open annulene structure as a mixture of two diastereoisomers.…”

Organocatalytic transformations of alkynals, alkynones, propriolates, and related electron-deficient alkynes

“…The reaction in presence of tributyl-or tricyclohexylphosphine led to the corresponding cyclopentenes in low yields (23%). 95 These phosphine-catalyzed [3þ2] cycloadditions have also been used to synthesize spirocyclic skeletons, which are very important structures because they are present in a great number of natural products. Lu and co-workers studied the cycloaddition reactions of 2-methylene-cycloalkanones 183 with tert-butyl 2-butynoates 182 catalyzed by tributylphosphine to obtain the spirocycles 184/185 in high yields and regioselectivities (Scheme 80).…”