102619-08-9Relevant articles and documents
Palladium-catalyzed decarboxylative asymmetric allylic alkylation of enol carbonates
Trost, Barry M.,Xu, Jiayi,Schmidt, Thomas
supporting information; experimental part, p. 18343 - 18357 (2010/04/25)
Palladium-catalyzed decarboxylative asymmetric allylic alkylation (DAAA) of allyl enol carbonates as a highly chemo-, regio-, and enantioselective process for the synthesis of ketones bearing either a quaternary or a tertiary R-stereogenic center has been investigated in detail. Chiral ligand L4 was found to be optimal in the DAAA of a broad scope of cyclic and acyclic ketones including simple aliphatic ketones with more than one enolizable proton. The allyl moiety of the carbonates has been extended to a variety of cyclic or acyclic disubstituted allyl groups. Our mechanistic studies reveal that, similar to the direct allylation of lithium enolates, the DAAA reaction proceeds through an "outer sphere" S N2 type of attack on the π-allylpalladium complex by the enolate. An important difference between the DAAA reaction and the direct allylation of lithium enolates is that in the DAAA reaction, the nucleophile and the electrophile were generated simultaneously. Since the π-allylpalladium cation must serve as the counterion for the enolate, the enolate probably exists as a tight-ion-pair. This largely prevents the common side reactions of enolates associated with the equilibrium between different enolates. The much milder reaction conditions as well as the much broader substrate scope also represent the advantages of the DAAA reaction over the direct allylation of preformed metal enolates.
Photochemical Transformations, 65. The 3? -> 3?-Route to 1H-Azepines/Benzene Imines
Prinzbach, Horst,Bringmann, Horst,Fritz, Hans,Markert, Juergen,Knothe, Lothar,et al.
, p. 616 - 644 (2007/10/02)
With several newly prepared substrates the influence of substituents upon the individual steps in the 3? -> 3?-route to 1H-azepines is more precisely defined: The C-unsubstituted 7-azanorbornadiene 2a, its 2,3-dichloro derivative 2b, the dimethyl 5,6-dichloro-2,3-dicarboxylate 2c, and the diesters 2d, e with dipolarophilic groups at C-1/N-7 are selectively isomerized by sensitized/direct photoexcitation into the azaquadricyclanes 29a-e, some of which are highly unstable.For the thermal conversion of the basic skeleton (N-Tos)29a the kinetic parameters have been determined (benzene): Ea = 28.0 +/- 0.2 kcal/mol, lg A = 15.7; ΔH* = 27.3 +/- 0.2 kcal/mol, ΔS* = 11.1 +/- 0.7 e.u.This barrier is lowered more efficiently by the chloro (29b, c) than by the methoxycarbonyl substituents (29f), with the former (latter) causing exclusive scission of the opposite (neighbouring) cyclopropane bonds.The intermediate azomethine ylides are captured with dipolarophilic reagents more or less efficiently depending on their substitution pattern.In the case of 29d(28d) the intramolecular addition of the unactivated yne component (37) at -30C is so fast, that azepine formation is almost totally suppressed (?2 + ?2 + Σ2>, 36?).The azepine/benzene imine equilibrium mixture 31c 32c (ca. 90:10) crystallizes as 31c (X-ray crystal structure analysis).
