Thermal and Fe(II)-catalyzed decompn. of NH3OSO3 in the presence of alkyl ethers and protonated heteroarom. bases affords α-alkylation products of the base with high selectivity and yield. The reaction is a radical redox-chain process involving the formation of ammoniumyl radicals (NH3+•), preferential H abstraction from α-C-H bonds of ether by NH3+•, trapping of the nucleophilic alkyl radical produced by the base and oxidn. of the pyridinyl radical adduct by NH3OSO3 or Fe(III). Thermal initiation appears to be somewhat less efficient than Fe(II) or Fe(III) initiation. The α-oxyalkylation process appears to be strongly affected by the reducing properties of the C free radicals, their reversibility in the addn. to the base and by hydrolysis of NH3OSO3. The selectivity of the H atom abstraction by NH3+• and the competition of the free radical intermediates between addn. to the base and oxidn. by Fe(III) have been investigated
Hydroxylamine-O-sulfonic acid-induced substitution of heteroaromatic bases by α-oxyalkyl radicals from alkyl ethers
CITTERIO, ATTILIO;
1985-01-01
Abstract
Thermal and Fe(II)-catalyzed decompn. of NH3OSO3 in the presence of alkyl ethers and protonated heteroarom. bases affords α-alkylation products of the base with high selectivity and yield. The reaction is a radical redox-chain process involving the formation of ammoniumyl radicals (NH3+•), preferential H abstraction from α-C-H bonds of ether by NH3+•, trapping of the nucleophilic alkyl radical produced by the base and oxidn. of the pyridinyl radical adduct by NH3OSO3 or Fe(III). Thermal initiation appears to be somewhat less efficient than Fe(II) or Fe(III) initiation. The α-oxyalkylation process appears to be strongly affected by the reducing properties of the C free radicals, their reversibility in the addn. to the base and by hydrolysis of NH3OSO3. The selectivity of the H atom abstraction by NH3+• and the competition of the free radical intermediates between addn. to the base and oxidn. by Fe(III) have been investigatedI documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
