Formation and Reactions of Bicyclo[1.1.1]pentyl-1 Cations
摘要:
The ionization of l-bicyclo[1.1.1]pentyl halides was shown to initially form the 1,3-bridged bicycle[1.1.1]pentyl-l cation. It appears to be a transition state that leads to the bicyclo[1.1.0]butyl-1-carbinyl cation which can be trapped with azide ion and can be directly observed by NMR in SO2CIF. Although the major products of solvolysis of the halides are 3-methylenecyclobutyl derivatives, the corresponding cation was calculated to have a significantly higher energy than the bicyclobutylcarbinyl ion. Therefore, the products are probably formed by an attack of the nucleophile on the latter ion, accompanied by bond migration. The bridgehead iodide reacts under solvolytic conditions with azide ion to form bicyclo[1.1.0]butyl-l azide as a product. It also reacts with potassium hydroxide to give [1.1.1]propellane, and the same reaction occurs on dissolving in acetonitrile or pyridine. The reaction of 1,3-diiodobicyclo[1.1.1]pentane with ethoxide ion also was found to give [1.1.1]propellane via a nucleophilic attack on one of the iodines. The propellane reacts with methyl hypoiodite to give 3-iodobicyclo[1.1.1]pentyl-l cation, which can react with methanol to give 3-methoxybicyclo[1.1.1]pentyl-l iodide and with azide ion to give 3-iodobicyclo[1.1.1]pentyl-1 azide. These data provide evidence for a discrete 3-iodobicyclo[1.1.1]pentyl-l cation intermediate. The effect of substituents on the rate of solvolysis of bicyclo[1.1.1]pentyl-l iodide was studied. With 3-aryl substituents, a value of rho = -1.7 was found, which is similar to that observed in the solvolysis of 3-arylcyclobutyl tosylates (rho = -1.6). The 3-substituted bicyclopentyl halides usually form the corresponding 3-methylenecyclobutyl cations rather than bicyclo[1.1.0]butyl-1-carbinyl ions, because most substituents will help stabilize the former type of ion.
formation of organozincreagents and subsequent cross-coupling with aryl halides and activated carboxylic acids is reported. Formation of organozincreagents is achieved by pumping organic halides, in the presence of ZnCl2 and LiCl, through an activated Mg-packed column under flow conditions. This method provides efficient in situ formation of aryl, primary, secondary, and tertiary alkyl organozinc reagents
Control of Redox‐Active Ester Reactivity Enables a General Cross‐Electrophile Approach to Access Arylated Strained Rings**
作者:Daniel C. Salgueiro、Benjamin K. Chi、Ilia A. Guzei、Pablo García‐Reynaga、Daniel J. Weix
DOI:10.1002/anie.202205673
日期:2022.8.15
Aliphatic strained rings can be (hetero)arylated through a decarboxylative cross-electrophile coupling. The keys to this advance are: 1) a new ligand that enables tolerance of a variety of strained ring classes and 2) electronic tunability of redox-active esters to control the rate of radical generation.
Synthesis of doubly bridgehead substituted bicyclo[1.1.1]pentanes. Radical transformations of bridgehead halides and carboxylic acids
作者:Piotr Kaszynski、Neil D. McMurdie、Josef Michl
DOI:10.1021/jo00001a058
日期:1991.1
Synthetic transformations of the 1-bicyclo[1.1.1]pentyl bridgehead radicals 11 generated from the corresponding bridgehead iodides 3 and carboxylic acids 5 are described. The relatively high nucleophilicity of these radicals was utilized in reactions with carbonyl compounds. In the reaction sequence of preparation of the iodides 3 and their further transformations, [1.1.1]propellane (2) is a synthetic equivalent of the recently described bicyclo[1.1.1]penta-1,3-dienyl dianion (8).
KASZYNSKI, PIOTR;MCMURDIE, NEIL D.;MICHL, JOSEF, J. ORG. CHEM., 56,(1991) N, C. 307-316
作者:KASZYNSKI, PIOTR、MCMURDIE, NEIL D.、MICHL, JOSEF