116783-31-4Relevant articles and documents
New insights into the mechanism of palladium-catalyzed allylic amination
Watson, Iain D. G.,Yudin, Andrei K.
, p. 17516 - 17529 (2007/10/03)
A comparative investigation into palladium-catalyzed allylic amination of unsubstituted aziridines and secondary amines has been carried out. The use of NH aziridines as nucleophiles favors formation of valuable branched products in the case of aliphatic allyl acetates. The regioselectivity of this reaction is opposite to that observed when other amines are used as nucleophiles. Our study provides evidence for the palladium-catalyzed isomerization of the branched (kinetic) product formed with common secondary amines into the thermodynamic (linear) product. In contrast, the branched allyl products obtained from unsubstituted aziridines do not undergo the isomerization process. Crossover experiments indicate that the isomerization of branched allylamines is bimolecular and is catalyzed by Pd0. The reaction has significant solvent effect, giving the highest branched-to-linear ratios in THF. This finding can be explained by invoking the intermediacy of σ-complexes, which is consistent with NMR data. The apparent stability of branched allyl aziridines towards palladium-catalyzed isomerization is attributed to a combination of factors that stem from a higher degree of s-character of the aziridine nitrogen compared to other amines. The reaction allows for regio- and enantioselective incorporation of aziridine rings into appropriately functionalized building blocks. The resulting methodology addresses an important issue of forming quaternary carbon centers next to nitrogen. The new insights into the mechanism of palladium-catalyzed allylic amination obtained in this study should facilitate synthesis of complex heterocycles, design of new ligands to control branched-to-linear ratio, as well as absolute stereochemistry of allylamines.
Mitsunobu Reaction of Unbiased Cyclic Allylic Alcohols
Shull, Brian K.,Sakai, Takashi,Nichols, Jeffrey B.,Koreeda, Masato
, p. 8294 - 8303 (2007/10/03)
The stereochemical inversion of unbiased allylic alcohols using triphenylphosphine, diethyl azodicarboxylate, and benzoic acid, commonly known as the Mitsunobu reaction, was studied in three different solvents with specific attention toward the product composition. The results generated for the Mitsunobu reaction of (R)-3-deuterio-2-cyclohexen-1-ol and the cis and trans isomers of 1-deuterio-5-methyl-2-cyclohexen-1-ol, 1-deuterio-5-tert-butyl-2-cyclohexen-1-ol, and optically active cis and trans 5-isopropyl-2-methyl-2-cyclohexen-1-ol all gave similar product distributions with respect to inversion and retention at the carbinol center as well-as syn and anti Sn2′ type addition when THF or benzene was used as the solvent (CH2Cl2 gave less selective product distributions). Interestingly, it was found that the quasi-equatorial and quasi-axial nature of the starting allylic alcohol does not appear to affect the product distribution for this reaction, nor does methyl substitution at the central carbon of the allylic alcohol. In all cases, significant amounts (8-28%) of non-SN2 type products were detected for these sterically unbiased allylic alcohols; only 72-77% of the product was from SN2 type reaction when sterically undemanding (R)-S-deuterio-2-cyclohexen-1-ol was subjected to Mitsunobu conditions.
REGIO- AND STEREO-CHEMISTRY IN ALLYLATION OF ARYL GRINARD REAGENTS CATALYZED BY PHOSPHINE-NICKEL AND -PALLADIUM COMPLEXES
Hayashi, Tamio,Konishi, Mitsuo,Yokota, Kan-Ichi,Kumada, Makoto
, p. 359 - 374 (2007/10/02)
Nickel and palladium complexes with the 1,1'-bis(diphenylphosphino)ferrocene ligand effectively catalyze regioselective cross-coupling of allylic ethers such as 1- or 3-methyl-2-propenyl silyl ethers with aryl-Grinard reagents, where the nickel catalyst l
