0000000000043012
AUTHOR
Paula Bello
Gold catalyzed stereoselective tandem hydroamination–formal aza-Diels–Alder reaction of propargylic amino esters
A gold-catalyzed tandem intramolecular hydroamination-formal aza-Diels-Alder reaction of propargylic amino esters is described. The overall process leads to the formation of a tetracyclic framework as a single diastereoisomer, with the creation of four bonds and five stereocenters.
ChemInform Abstract: Gold Catalyzed Stereoselective Tandem Hydroamination-Formal Aza-Diels-Alder Reaction of Propargylic Amino Esters.
The overall sequence of the tandem reaction presented here leads to nitrogen-containing tetracycles under formation of 4 bonds and five stereocenters, in most cases as single diastereoisomers.
One-pot cross-enyne metathesis (CEYM)-Diels-Alder reaction of gem-difluoropropargylic alkynes.
Propargylic difluorides 1 were used as starting substrates in a combination of cross-enyne metathesis and Diels–Alder reactions. Thus, the reaction of 1 with ethylene in the presence of 2nd generation Hoveyda–Grubbs catalyst generates a diene moiety which in situ reacts with a wide variety of dienophiles giving rise to a small family of new fluorinated carbo- and heterocyclic derivatives in moderate to good yields. This is a complementary protocol to the one previously described by our research group, which involved the use of 1,7-octadiene as an internal source of ethylene.
Synthesis of a New Fluorinated Oxazolidinone and Its Reactivity as a Chiral Auxiliary in Aldol Reactions.
A new enantiomerically pure fluorinated oxazolidinone has been prepared from a fluorinated imidoyl chloride and an optically pure sulfoxide. The diastereoselective reduction of the β-iminosulfoxide thus formed followed by elimination of the sulfoxide and cyclization of the created aminoalcohol furnishes the desired product. The fluorinated oxazolidinone was subsequently used as a chiral auxiliary in Aldol reactions. We also found that the selective formation of the syn-Evans and syn-non-Evans diastereoisomer can be controlled by adjusting the Lewis acid/base ratio.
1,7-Octadiene-Assisted Tandem Multicomponent Cross-Enyne Metathesis (CEYM)-Diels-Alder Reactions: A Useful Alternative to Mori’s Conditions
The use of 1,7-octadiene as an in situ source of ethylene led us to develop a novel multicomponent tandem cross-enyne metathesis (CEYM)-Diels-Alder reaction. The process can be considered a relay metathesis, in which the ethylene liberated in the ring-closing metathesis (RCM) of 1,7-octadiene initiates the tandem sequence. Aliphatic, aromatic, and fluorinated alkynes and several dienophiles are compatible with the process, which is particularly efficient with aromatic alkynes. This methodology constitutes a useful variant of Mori's conditions in CEYM-related reactions.
AuX3-Mediated Selective Head-to-Head Dimerization of Difluoropropargyl Amides
A dimerization of difluoropropargyl amides by reaction with gold(III) halides is described. A reductive elimination of a divinylgold species can be invoked to rationalize its formation. Initial studies of the unusual reactivity of these 1,4-dihalo-1,3-dienes have been performed.
ChemInform Abstract: 1,7-Octadiene-Assisted Tandem Multicomponent Cross-Enyne Metathesis (CEYM)-Diels-Alder Reactions: A Useful Alternative to Mori′s Conditions.
The protocol relies on a relay metathesis process, in which 1,7-octadiene acts as an in situ source of ethylene.