Recent developments in allene chemistry

Stereochemistry of the Asymmetric Carbopalladation of Allenes Followed by Nucleophilic Substitution Reactions with Carbo- and Aminonucleophiles

“…Then, a solution of (Ϯ)-1-phenyl-1,2-butadiene (6) (60 mg, 0.46 mmol) in THF (1 ml) was further added and the reaction mixture was stirred for 30 min. This solution was added to the above solution and the reaction mixture was heated under reflux for 18 h. The reaction mixture was diluted with ether, and the solution was washed with a saturated aqueous NH 4 Cl and a saturated aqueous NaCl, dried over anhydrous Na 2 SO 4 , and concentrated under reduced pressure. The residue was submitted to preparative TLC (ether-hexane 1 : 2) to give dimethyl (S)-(Ϫ)-(1,2-diphenyl-1-buten-3-yl)propanedioate (9) (51 mg, 33% yield, 88% e.e.…”

“…The results obtained under other reaction conditions are summarized in Tables 1 and 2. (S) Determination of the Absolute Configuration of 9 by Chemical Correlation. Oxidative Cleavage of (؊)-9 A 1.57 N THF solution (0.3 ml) of OsO 4 , and NaIO 4 (458 mg, 2.14 mmol) were added to a solution of (Ϫ)-9 (361 mg, 1.07 mmol, 83% e.e.) in ether (2 ml)-H 2 O (2 ml), and the reaction mixture was stirred at room temperature for 48 h. The reaction mixture was diluted with ether, and the solution was washed with a saturated aqueous NaCl, dried over anhydrous Na 2 SO 4 , and concentrated under reduced pressure.…”

“…To the above flask THF (4 ml) was added and the mixture was stirred for 30 min. A solution of (R)-6 (92 mg, 0.71 mmol) in THF (6 ml) was added and the reaction mixture was heated under reflux for 12 h. The reaction mixture was diluted with ether, and the solution was washed with a saturated aqueous NH 4 Cl and a saturated aqueous NaCl, dried over anhydrous Na 2 SO 4 , and concentrated under reduced pressure. The residue was submitted to preparative TLC (ethyl acetate-hexane 1 : 20) to give (E)-4-benzylidene-3-methyl-1,2,3,4-tetrahydro-2-oxanaphthalene (24) (65 mg, 43% yield).…”

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An allene functionality has received much interest for introducing a three-carbon unit in organic synthesis, [1][2][3][4][5] especially as a good chiral regulator with the axial chirality in asymmetric synthesis. 6,7) The axial chirality has received much attention for the stereochemical characteristics, and many methodologies of the asymmetric synthesis of allenes with the axial chirality have been reported so far.

8) Currently, the use of the allene functionality in transition metal-catalyzed reactions has become of great importance from the synthetic and theoretical points of view with regard to the chemical characteristics associated with the axial chirality.

9-12) Therefore, an allene with the axial chirality might be a synthetically useful chiral director for the elaboration of chiral complex organic molecules in asymmetric synthesis with metal catalysts.

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“…An allene functionality has received much interest for introducing a three-carbon unit in organic synthesis, [1][2][3][4][5] especially as a good chiral regulator with the axial chirality in asymmetric synthesis. 6,7) The axial chirality has received much attention for the stereochemical characteristics, and many methodologies of the asymmetric synthesis of allenes with the axial chirality have been reported so far.…”