Straightforward and efficient: Functionalized eight‐membered carbocycles are easily obtained from simple allyl‐substituted 5‐hexyn‐1‐ol derivatives by a catalytic tandem sequence involving a 6‐exo cycloisomerization followed by a Prins‐type cyclization (see scheme).
An efficient method for the synthesis of [3.3.1]bicyclic compounds from easily available alkynol derivatives has been developed. The reaction is based on a gold- or platinum-catalyzed tandem process that involves an intramolecular hydroalkoxylation of a triple bond followed by a Prins-type cyclization. The reaction has been carried out with differently substituted alkynol derivatives and oxygen-, nitrogen-, and carbon-centered nucleophiles. The incorporation of halogen atoms as nucleophiles and elimination reactions has also been studied. Enantiomerically pure [3.3.1]bicyclic systems were easily synthesized from the chiral pool.
New solvent-assisted mechanistic routes were located for the (THF)W(CO)5-promoted endo- and exo-cycloisomerization of 4-pentyn-1-ol using the B3LYP/6-31G (with the LANL2DZ relativistic pseudopotential for W) theory level. A mixed model was used by explicitly including a THF molecule as a component of the reactive system and taking into account the effect of bulk solvent by means of the PCM-UAHF method. This THF molecule plays a crucial role by making the endo route leading to the cyclic carbene complex the most favorable one because of an important catalytic effect. These new mechanisms allow a satisfactory rationalization of experimental facts.
Anorganische Schichten: Graphenartiges MoS2 und WS2 wurde durch drei verschiedene chemische Methoden hergestellt. Mikroskopische Untersuchungen offenbarten, dass die Strukturen aus einer oder wenigen Schichten aufgebaut sind (siehe TEM‐Aufnahme von WS2‐Schichten), und ein atomar aufgelöstes TEM‐Bild zeigt, dass schichtförmiges MoS2 eine hexagonale Anordnung von Mo‐ und S‐Atomen aufweist (siehe Einschub).
Herein, we report an end-to-end process including synthesis,
work-up,
purification, and post-purification with minimal human intervention
using Negishi coupling as a key transformation to increase Fsp3 in bioactive molecules. The main advantages of this protocol
are twofold. First, the automated sequential generation of organozinc
reagents from readily available alkyl halides offers a large diversity
of alkyl groups to functionalize (hetero)aryl halide scaffolds via Pd-catalyzed Negishi coupling in continuous flow. Second,
a fully automated liquid–liquid extraction has been developed
and successfully applied for unattended operations. The workflow was
completed with mass-triggered preparative high-performance liquid
chromatography HPLC, providing an efficient production line of compounds
with enriched sp3 character and better drug-like properties.
The modular nature allows a smooth adaptation to a wide variety of
synthetic methods and protocols and makes it applicable to any medchem
laboratory.
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