A palladium-catalyzed, norbornene-mediated Catellani ortho-acylation reaction was developed by the use of either acyl chlorides or acid anhydrides as acylation reagents. The addition of more than a stoichiometric amount of H2 O is crucial for this transformation when acid chlorides are used, and kinetic studies indicate that the active acylation reagent is possibly an acid anhydride.
A palladium-catalyzed asymmetric synthesis of planar chiral metallocene compounds is reported. The reaction stereoselectively functionalized one of the ortho C-H bonds of Cp rings by intramolecular cyclization to form indenone derivatives in high yields with excellent enantioselectivity. The mild set of reaction conditions allowed a wide variety of chiral metallocene compounds to be synthesized with broad functional group tolerance. The influences of preinstalled chiralities on the other Cp-ring were also investigated.
A palladium-catalyzed Heck-type cascade reaction of aryl halides and N-tosyl hydrazones is reported. The neopentylpalladium species, generated from an intramolecular Heck-type insertion reaction of aryl halides, could efficiently react with carbenes to form highly functionalized alkenes. The synthesis of spiro compounds was also explored via a multiple Heck-type insertion reaction with N-tosyl hydrazone.
This norbornene-mediated acylation reaction uses acyl chlorides as acylating reagents. The addition of an excess of water is crucial for the transformation. It is proposed, that the active acylating reagent is an in-situ-generated acid anhydride. -(HUANG, Y.; ZHU, R.; ZHAO, K.; GU*
Tin
perovskites have received great concern in solar cell research
owing to their favorable optoelectronic performance and environmental
friendliness. However, due to their poor crystallization and easy
oxidation, the performance improvement for tin-based perovskite solar
cells (TPSCs) is rather challenging. Herein, reductive 3-hydroxytyramine
hydrochloride (DACl) with NH2·HCl and phenol groups
as co-additives with SnF2 is added into the precursor to
modulate perovskite crystallization and inhibit Sn2+ oxidation
for high-performance TPSCs. The Lewis base group of NH2 HCl in DACl could bind to perovskite lattices to modulate the crystallization
with suppressed defects in the bulk and grain boundary, whereas reductive
phenol groups effectively constrain the Sn2+ oxidation.
Moreover, the undissociated DACl decreases the supersaturated concentration
of tin perovskite solution and creates a pre-nucleation site for rapid
nucleation to further regulate crystallization. Consequently, the
DACl-derived TPSCs achieve a high power-conversion efficiency (PCE)
that reaches up to 11%. More impressively, the device remains at 84%
of the initial PCE after full-sun illumination in N2 over
600 h without being encapsulated. This DACl-based synergistic modulation
of a lead-free perovskite demonstrates a feasible approach using one
molecule with different functional groups to manipulate crystallization,
Sn2+ oxidation, and defect reparation of tin perovskite
films, providing a critical guideline for constructing high-quality
perovskites by multifunctional additives with high photovoltaic performance.
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