A Direct Synthesis of Allenes by a Traceless Petasis Reaction

Stereoselective, Ag-Catalyzed Cyclizations To Access Polysubstituted Pyran Ring Systems: Synthesis of C1-C12 Subunit of Madeirolide A

The exploration into the scope of a silver-catalyzed cyclization (AgCC) of propargyl benzoates for accessing pyran ring systems has been reported. The impact of the degree of substitution, nature of the substitution on the carbon backbone/benzoate moiety, and stereochemistry has been evaluated. The application of this methodology to the synthesis of the C1-C12 southern fragment of madeirolide A is disclosed.

Asymmetric Protonation of Cumulenolates: Synthesis of Allenyl Aldehydes Facilitated by an Organomanganese Auxiliary

Chiral ammonium salts were used to catalyze the isomerization of organomanganese-complexed alkynyl aldehydes to chiral allenal building blocks in moderate to good enantiomeric excesses. Normally, conjugated alkynyl aldehydes do not isomerize to their thermodynamically less stable allene isomers. However, with a manganese auxiliary in place to promote allene formation, asymmetric protonation of cumulenolate intermediates was realized using a variety of cinchonidinium salts in a weakly basic biphasic reaction system. Optimal results were realized using a novel cinchonidinium geranyl derivative with its C-9 hydroxyl group playing a crucial role in enantioselectivity.

Rapid synthesis of alkylaminophenols via the Petasis borono–Mannich reaction using protonated trititanate nanotubes as robust solid–acid catalysts

The Petasis borono–Mannich reaction was applied to the synthesis of alkylaminophenols from o-hydroxybenzaldehydes, secondary amines and boronic acids in the presence of H₂Ti₃O₇ nanotubes as reusable solid–acid catalysts.

Cu-Catalyzed hydrophosphorylative ring opening of propargyl epoxides: highly selective access to 4-phosphoryl 2,3-allenols

A CuI-catalyzed cross-coupling of propargyl epoxides with P(O)H compounds to produce 4-phosphoryl 2,3-allenols with excellent selectivity under mild conditions is disclosed.

Chemo- and regioselective reductive transposition of allylic alcohol derivatives via iridium or rhodium catalysis

We report highly chemo- and regioselective reductive transpositions of methyl carbonates to furnish olefin products with complementary regioselectivity to that of established Pd-catalysis.

SAMDI Mass Spectrometry-Enabled High-Throughput Optimization of a Traceless Petasis Reaction

Development of the self-assembled monolayer/MALDI mass spectrometry (SAMDI) platform to enable a high-throughput optimization of a traceless Petasis reaction is described. More than 1800 unique reactions were conducted simultaneously on an array of self-assembled monolayers of alkanethiolates on gold to arrive at optimized conditions, which were then successfully transferred to the solution phase. The utility of this reaction was validated by the efficient synthesis of a variety of di- and trisubstituted allenes.

Organo-manganese η2-auxiliary directed reactions: a diastereoselective approach to 2,3-allenols

Propargyl aldehydes underwent isomerization to allenyl aldehydes under mildly basic conditions when complexed to an organo-manganese auxiliary using methylcyclopentadienyl manganese tricarbonyl (MMT). This traceless auxiliary magnifies the axial chirality of the allene moiety, allowing for highly diastereoselective additions to the aldehyde carbonyl and subsequent access to an array of 2,3-allenols. Using this strategy, a nitrile-substituted 2,3-allenol was prepared and efficiently converted to Hagen's gland lactone.

Dehydrative thiolation of allenols: indium vs gold catalysis

Intermolecular additions of thiols to allenols via formal S(N)2' selectivity to produce functionalized dienes are described. Although this dehydrative reaction was initially developed using gold(I) catalysis, indium(III) proves to be a far superior catalyst in terms of selectivity and substrate scope.

Synthesis of tertiary propargylamines via a rationally designed multicomponent reaction of primary amines, formaldehyde, arylboronic acids and alkynes

A novel approach for the synthesis of tertiary propargylamines is achieved through a Cu(OAc)₂-catalyzed multicomponent reaction of primary amines, formaldehyde, arylboronic acids and alkynes.