Iridium‐Catalyzed 1,3‐Hydrogen Shift/Chlorination of Allylic Alcohols

Abstract

α‐Chlorketone und α‐Chloraldehyde werden in der aus 1,3‐H‐Wanderung und C‐Cl‐Bindungsbildung bestehenden Tandemreaktion von Allylalkoholen mit N‐Chlorsuccinimid (NCS) erhalten. Die Reaktion liefert mit vollständiger Selektivität ein einzelnes Konstitutionsisomer monochlorierter Carbonylverbindungen. Die Synthese 4,5‐disubstituierter 2‐Aminothiazole ausgehend von Allylalkoholen illustriert die Nützlichkeit der Transformation.

Photoregulation of α‐Chymotrypsin Activity by Spiropyran‐Based Inhibitors in Solution and Attached to an Optical Fiber

“…α‐Bromocarbonyl compounds contain two consecutive electrophilic carbon atoms, which makes them important precursors in the synthesis of a variety of heterocyclic compounds. For example, treatment of 3 f with thiourea afforded 2‐aminothiazole 7 in excellent yield 6c. Additionally, reduction of the carbonyl functional group of α‐bromocarbonyls affords another highly versatile building block in organic synthesis.…”

“…During the last few years, we have reported alternative selective methods for the synthesis of α‐fluoro6a–b and α‐chloro ketones and aldehydes6c in excellent yields and under mild reaction conditions. The methodology formally relies on the formation of in situ catalytic amounts of enolates from allylic alcohols.…”

Highly Functionalized and Potent Antiviral Cyclopentane Derivatives Formed by a Tandem Process Consisting of Organometallic, Transition‐Metal‐Catalyzed, and Radical Reaction Steps

“…The detailed mechanism of action for these compounds requires further studies. The mechanistic course and the diastereoselectivity can be rationalized as follows (Scheme 6): Nucleophilic addition of aryllithium compounds 1 to unsaturated aldehydes 2 generates allylic alkoxides 3, which enter the ruthenium-catalyzed isomerization cycle [5][6][7][8][9][10] by a transmetalation to the ruthenium alkoxides 13. Hydride transfer to ruthenium leads to complexes 14 A or 14 B with the coordinated enone unit.…”

Synthesis of α‐Iodoketones from Allylic Alcohols through Aerobic Oxidative Iodination

“…Both catalysts, iridium complex II and NaNO2, were found to be essential for the formation of the desired product (entries 8 and 9, respectively). Replacement of I2 by NIS or KI under otherwise identical reaction conditions did not give the product either (entries [10][11]. The reaction conditions of entry 7 were chosen as the optimal conditions for studying the substrate scope, i.e., 0.5 equiv.…”

“…The reaction of the allylic alcohol with the iridium catalyst [11,13] and molecular iodine gives the corresponding a-iodoketone. [6,10] HI is formed as a byproduct, which in turn protonates NaNO2 to give nitrous acid. Rapid decomposition of HNO2 gives NO2, a good oxidant that acts as an electron-transfer mediator in the oxidation of iodide by oxygen, the stoichiometric oxidant.…”