Vinylphosphonium Salts and Allenes from Carbonyl Compounds Using Titanium-Substituted Ylides

Area of Science:

• Organic Chemistry
• Organometallic Chemistry
• Synthetic Methodology

Background:

• Vinylphosphonium salts are versatile synthetic intermediates.
• Efficient synthesis of 1,3-disubstituted allenes remains a challenge in organic chemistry.

Purpose of the Study:

• To develop a convenient method for synthesizing (E)-vinylphosphonium salts.
• To establish a facile route for the synthesis of 1,3-disubstituted allenes.

Main Methods:

• Reaction of carbonyl compounds with titanium-substituted ylide species, specifically (Me(2)N)(3)P=CHTi(OiPr)Cl(2) or (Me(2)N)(3)P=CHTi(OiPr)(2)Cl.
• Conversion of vinylphosphonium salts to allenes via deprotonation and condensation with a second aldehyde.
• In situ generation of the metal-substituted ylide reagent from commercially available materials.

Main Results:

• The reaction provides convenient access to (E)-vinylphosphonium salts from nonenolizable aldehydes and activated or unhindered ketones.
• A two-step double olefination strategy allows for the synthesis of 1,3-disubstituted allenes.
• Two representative vinylphosphonium salts exhibited reversible isomerization to the (Z)-form upon irradiation.

Conclusions:

• The developed methodology offers a highly convenient route for synthesizing 1,3-disubstituted allenes.
• This approach, combined with a prior one-pot reaction, represents the most accessible pathway for these compounds.
• The metal-substituted ylide reagent can be prepared efficiently in situ.