Observation of the First Heck-Type Cross-Coupling Reaction of Allenes with Aryl Halides. Synthesis of Polysubstituted 1,2-Allenyl Sulfones

The Heck-type allenylation of aryl halides with allenes has been observed for the first time:  The regioselectivity of intermolecular carbopalladation of 1,2-allenyl sulfones affording vinylic Pd intermediates is completely opposite to what was reported in the literature

Highly Regio- and Stereoselective Synthesis of 2(<i>E</i>),4-Alkadienoates via the Pd(0)-Catalyzed Reaction of Aryl Halides with 3,4-Alkadienoates

2(E),4-Alkadienoates were prepared highly stereoselectively via the Pd(0)/Ag2CO3-cocatalyzed reaction of 3,4-alkadienoates and aryl halides. The reaction is believed to proceed via the oxidative addition−carbopalladation−β-H elimination process. Compared to the other reported methods for the synthesis of 2,4-alkadienoates, in which usually only disubstituted CC bonds were formed, the current reaction forms the trisubstituted or even tetrasubstituted CC bond highly stereoselectively

Iron-Catalyzed Unexpected Easy Access to Stereodefined Trimethylsilyl Vinyl Ketenes

Stereodefined trimethylsilyl vinyl ketenes with polysubstitution have been synthesized highly regio- and stereoselectively via an iron-catalyzed reaction of 2-trimethylsilyl-2,3-allenoates with Grignard reagents in good to excellent yields. The reaction was believed to proceed via a conjugate addition and elimination mechanism. Applications of the products for the synthesis of stereodefined α-silyl-β,γ-unsaturated enones, a stereodefined triene, and polysubstituted phenols have been carefully demonstrated

A Novel Synthesis of 1,3-Oxazine-2,4-diones via a Simple and Efficient Reaction of CO₂ with 2,3-Allenamides

A simple and efficient reaction of CO2 with 2,3-allenamides under mild conditions (CO2 balloon without any metal catalyst in the presence of K2CO3 or Cs2CO3) leads to an efficient synthesis of 1,3-oxazine-2,4-diones. The high reactivity of the allene moiety is crucial for the success of this transformation since the corresponding reaction of α,β-unsaturated alkenamides or alkynamides does not occur

Electrophilic Interaction of 2,3-Allenoates with PhSeCl. An Unexpected Highly Stereoselective Synthesis of 3-Phenylseleno-4-oxo-2(<i>E</i>)-alkenoates

We have previously reported an efficient synthesis of β-phenylselenium-substituted butenolides via electrophilic cyclization of 2,3-allenoates with PhSeCl in aqueous MeCN. However, when 2,3-allenoates were treated with PhSeCl in MeCN, 3-phenylseleno-4-oxo-2(E)-alkenoates were formed unexpectedly. The addition of Li2CO3 improved the yield and the selectivity of the reaction. A possible mechanism involving a decomposition of selenate esters was proposed

Highly Stereoselective Facile Synthesis of 2-Acetoxy-1,3(<i>E</i>)-alkadienes via a Rh(I)-Catalyzed Isomerization of 2,3-Allenyl Carboxylates

A highly stereoselective Rh(I)-catalyzed 1,3-acetoxyl rearrangement of 1,2-allen-3-yl carboxylates leading to 2-acetoxy-1,3(E)-alkadienes has been developed. In addition to the high catalytic efficiency and the scope, the excellent E-selectivity of the double bond is remarkable

Electrophilic Interaction of 2,3-Allenoates with PhSeCl. An Unexpected Highly Stereoselective Synthesis of 3-Phenylseleno-4-oxo-2(<i>E</i>)-alkenoates

We have previously reported an efficient synthesis of β-phenylselenium-substituted butenolides via electrophilic cyclization of 2,3-allenoates with PhSeCl in aqueous MeCN. However, when 2,3-allenoates were treated with PhSeCl in MeCN, 3-phenylseleno-4-oxo-2(E)-alkenoates were formed unexpectedly. The addition of Li2CO3 improved the yield and the selectivity of the reaction. A possible mechanism involving a decomposition of selenate esters was proposed

A Novel Synthesis of 1,3-Oxazine-2,4-diones via a Simple and Efficient Reaction of CO₂ with 2,3-Allenamides

A simple and efficient reaction of CO2 with 2,3-allenamides under mild conditions (CO2 balloon without any metal catalyst in the presence of K2CO3 or Cs2CO3) leads to an efficient synthesis of 1,3-oxazine-2,4-diones. The high reactivity of the allene moiety is crucial for the success of this transformation since the corresponding reaction of α,β-unsaturated alkenamides or alkynamides does not occur

Highly Stereoselective Facile Synthesis of 2-Acetoxy-1,3(<i>E</i>)-alkadienes via a Rh(I)-Catalyzed Isomerization of 2,3-Allenyl Carboxylates

A highly stereoselective Rh(I)-catalyzed 1,3-acetoxyl rearrangement of 1,2-allen-3-yl carboxylates leading to 2-acetoxy-1,3(E)-alkadienes has been developed. In addition to the high catalytic efficiency and the scope, the excellent E-selectivity of the double bond is remarkable

Highly Selective Mild Stepwise Allylation of <i>N</i>-Methoxybenzamides with Allenes

An efficient Rh­(III)-catalyzed stepwise ortho allylation of <i>N</i>-methoxybenzamides <b>1</b> with polysubstituted allenes is reported. This C–H functionalization involving allenes is conducted under very mild conditions (−20 °C or room temperature) and compatible with ambient air and moisture, and it can be applied to terminal or internal allenes with different synthetically attractive functional groups. Highly efficient axial chirality transfer has been realized, yielding optically active lactones