Enamide-olefin ring-closing metathesis

Amidopalladation of Alkoxyallenes Applied in the Synthesis of an Enantiopure 1-Ethylquinolizidine Frog Alkaloid

A palladium-catalyzed amidation of alkoxyallenes has been developed for the construction of linear allylic N,O-acetals under basic conditions involving (cyclic) amides, sulfonamides, carbamates, and amidophosphates. Application of the methodology provided access to the enantiopure 1-ethylquinolizidine structural motif, which is a key synthon in the synthesis of the naturally occurring poisonous frog quinolizidine 233A and derivatives such as the 1-epi-isomer of quinolizidine 207I.

The emergence of allenamides in organic synthesis

This Account highlights recent studies describing utility of allenamides in stereoselective inter- and intramolecular synthetic methodologies. It is written to raise interest in the chemistry of allenamides.

The first examples of ring-closing olefin metathesis of vinyl chlorides

[reaction: see text] Ring-closing metathesis (RCM) of olefinic vinyl chlorides can be effected by using the second generation Grubbs catalyst (10 mol %, PhH, 65 degrees C) to produce a variety of carbocyclic and heterocyclic five-, six-, and seven-membered rings in excellent yields.

Relative rate profile for ring-closing metathesis of a series of 1-substituted 1,7-octadienes as promoted by a 4,5-dihydroimidazol-2-ylidene-coordinated ruthenium catalyst

[reaction: see text] This report details the kinetic responses of nine compounds of type 6 to ring-closing metathesis as promoted by 2 to give the identical product 7. The experimental observations have been subjected to Hammett analysis. The rho value for the composite aromatic derivatives (R = p-XC(6)H(4)-) differs from that of the aliphatic series, although both are negative because electron-donating groups accelerate the reaction.

New tandem catalysis: preparation of cyclic enol ethers through a ruthenium-catalyzed ring-closing metathesis-olefin isomerization sequence

Tandem reactions that proceed with a single metal catalyst precursor offer novel opportunities for developing efficient new reaction sequences. In this regard, reaction conditions have been identified that allows for a tandem ring-closing metathesis-olefin isomerization sequence catalyzed by a common ruthenium precursor. Specifically, the tandem process generates cyclic enol ethers from a variety of readily available acyclic dienes in a single reaction vessel using Grubbs' ruthenium alkylidene.

A novel use of Grubbs' carbene. Application to the catalytic deprotection of tertiary allylamines

[reaction--see text] The first examples accounting for the catalytic deprotection of allylic amines by using reagents different from palladium catalysts have been achieved via Grubbs' carbene-mediated reaction. The current mechanistic hypothesis invokes a nitrogen-assisted ruthenium-catalyzed isomerization, followed by hydrolysis of the enamine intermediate. We believe that an unprecedented mode of ring opening of the ruthenacyclobutane was involved.