Free radical and palladium-catalysed hydrostannation of allenes: a comparison
作者:Terence N. Mitchell、Ulrich Schneider
DOI:10.1016/0022-328x(91)86272-r
日期:1991.3
While free radical hydrostannation of monosubstituted allenes with Me3SnH affords mixtures of varying composition, cyclohexylidene allene is attacked by the stannyl radical preferentially at the central carbon atom. In contrast, palladium-catalysed hydrostannation involves a regioselective attachment of the organotin moiety to the less highly substituted terminal carbon atom of the allene framework
Palladium Pincer Complex Catalyzed Stannyl and Silyl Transfer to Propargylic Substrates: Synthetic Scope and Mechanism
作者:Johan Kjellgren、Henrik Sundén、Kálmán J. Szabó
DOI:10.1021/ja043951b
日期:2005.2.1
corresponding pincer complex catalyst. DFT modeling studies have shown that the trimethylstannyl functionality is transferred to the propargylic substrate in a single reaction step with high allenyl selectivity. Inspection of the TS structures reveals that the trimethylstannyl group transfer is initiated by the attack of the palladium-tin sigma-bond electrons on the propargylic substrate. This is a novel
A number of allylic, allenylic and 2-propynylic (R′) derivatives of tin of the type R3SnR′ have been synthesized, and shown to undergo ready insertion of sulfurdioxide into the SnR′ bond. Rearrangement accompanies insertion so that the products have the alternate allylic, 2-propynylic and allenylic structures respectively. Di-insertion occurs only when groups attached to tin are quite susceptible
benzene or carbontetrachloridesolution. When R cis- or trans-2-butenyl(crotyl), 2-propynyl or 1,2-propadienyl (allenyl), the rearranged α-methallyl, allenyl or 2-propynyl thiocyanates, respectively, are produced. The reactions are quantitative as judged by direct PMR observations. When R possesses only moderate reactivity towards electrophiles, e.g., CH3 as in (CH3)4Sn, polymerisation of (SCN)2
Palladium Pincer Complex-Catalyzed Trimethyltin Substitution of Functionalized Propargylic Substrates. An Efficient Route to Propargyl- and Allenyl-Stannanes
作者:Johan Kjellgren、Henrik Sundén、Kálmán J. Szabó
DOI:10.1021/ja0391715
日期:2004.1.1
effects of the propargylicsubstrate: electron-withdrawing functionalities give mainly allenyl stannane products, while with electron-donating groups the main product is propargyl stannane. The catalytic reaction proceeds under very mild conditions tolerating many functionalities such as OH, OAc, NR3, and NR2Ac groups. Our mechanistic studies indicate that the key intermediate of the reaction is a monotrimethylstannane