The regioselective nitration of 9,9′-spirobifluorene
under
mild conditions is reported for the first time by operating under
Menke’s and Crivello’s conditions. The optimized protocol
allows obtaining 2-nitro and 2,2′-dinitro-9,9′-spirobifluorene
in yields of 79 and 95% and, for the first time, 2,2′,7-trinitro-9,9′-spirobifluorene
with 66% yield. Besides, the role of dinitrate salt in Crivello’s
protocol has been now clarified, which opens novel scenarios in the
preparation of functional materials.
The Suzuki–Miyaura cross-coupling reaction plays a fundamental role in modern synthetic organic chemistry, both in academia and industry. For this reason, scientists continue to search for new, more effective, cheaper and environmentally friendly procedures. Recently, micellar synthetic chemistry has been demonstrated to be an excellent strategy for achieving chemical transformations in a more efficient way, thanks to the creation of nanoreactors in aqueous environments using selected surfactants. In particular, the cheap and commercially available surfactant Kolliphor EL (a polyethoxylated castor oil derivative) has been used with success to achieve metal-catalyzed transformations in water with high yields and short reaction times, with the advantage of using air-sensitive catalysts without the need for inert atmosphere. In this work, the Kolliphor EL methodology was applied to the Suzuki cross-coupling reaction between thiophene and aniline, using the highly effective catalyst Pd(dtbpf)Cl2. The cross-coupling products were achieved at up to 98% yield, with reaction times of up to only 15 min, working at room temperature and without the need for inert atmosphere.
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