Facile and selective cleavage of allyl ethers, amines and esters using polymethylhydrosiloxane-ZnCl2/Pd(PPh3)4
S. Chandrasekhar*, Raji Reddy and R. Jagadeeshwar Rao
*Indian Institute of Chemical Technology, Hyderabad 500 007, India, Email:
srivaric
iict.ap.nic.in
S. Chandrasekhar, R. Reddy, R. J. Rao, Tetrahedron, 2001, 57, 3435-3438.
DOI: 10.1016/S0040-4020(01)00187-9
Abstract
Deprotection of allyl ethers, amines and esters to liberate hydroxyl, amino and acid groups is achieved under mild conditions. The reagent combination employed for this transformation is polymethylhydrosiloxane (PMHS), ZnCl2 and Pd(PPh3)4.
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Details
The document discusses a study conducted by S. Chandrasekhar, Ch. Raji Reddy, and R. Jagadeeshwar Rao at the Indian Institute of Chemical Technology, Hyderabad, on the selective cleavage of allyl ethers, amines, and esters. The researchers developed a mild and efficient method for deallylation using a combination of polymethylhydrosiloxane (PMHS), zinc chloride (ZnCl2), and tetrakis(triphenylphosphine)palladium(0) (Pd(PPh3)4). This method effectively liberates free hydroxy, amino, and acid groups from their corresponding allyl-protected forms under ambient conditions.
The study highlights the stability of the allyl group under both acidic and basic conditions, making it a popular protective group in organic synthesis. Traditional methods for removing allyl groups often involve harsh conditions or expensive reagents. The new method presented is advantageous due to its chemoselectivity, efficiency, economy, safety, and simplicity.
The researchers tested various substrates, including allyl ethers, amines, and esters, and achieved high yields of the deprotected products. The method was found to be compatible with a range of functional groups, demonstrating its potential utility in organic synthesis. The exact mechanism of the reaction remains unclear, but it likely involves the formation of a π-allyl palladium(II) complex and subsequent hydride transfer activated by zinc chloride.
Key Words
Allyl Ether, Deprotection (Ethers, Esters, Amines), Palladium Catalysis, π-allyl-palladium complex, PMHS
ID: J72-Y2001-470
