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The Enders SAMP/RAMP hydrazone alkylation reaction is an asymmetric carbon-carbon bond formation reaction facilitated by pyrrolidine chiral auxiliaries. It was pioneered by E. J. Corey and Dieter Enders in 1976, [1] and was further developed by Enders and his group. [2] This method is usually a three-step sequence.
The main metabolic steps are thought to be demethylenation followed by methylation of one hydroxy group, aromatic and side chain hydroxylation, oxidation of the pyrrolidine ring to the corresponding lactam as well as ring opening to the corresponding carboxylic acid.
An example of a [1,7]-electrocyclization of a diphenylethenyl-substituted azomethine ylide is shown below. This conrotatory ring-closing is followed by a suprafacial [1,5]-hydride shift, which affords the rearomatized product. The sterics and geometry of the reacting phenyl ring play a major role in the success of the reaction. [20]
Similarly, S. W. Baldwin and T. J. Doll examined a modification of the Hofmann–Löffler–Freytag reaction during their studies towards the synthesis of the alkaloid gelsemicine 41. The formation of the pyrrolidine ring of 40 was accomplished by irradiation of N-chloroamide 39. [19]
Pyrrolidine, also known as tetrahydropyrrole, is an organic compound with the molecular formula (CH 2) 4 NH. It is a cyclic secondary amine , also classified as a saturated heterocycle . It is a colourless liquid that is miscible with water and most organic solvents.
The polar reaction, N-cyclopentenyl pyrrolidine nucleophilic addition to the diazo compound, proceeds 1,500 times faster in polar DMSO than in non-polar decalin. On the other hand, a close analog of this reaction, N-cyclohexenyl pyrrolidine 1,3-dipolar cycloaddition to dimethyl diazomalonate, is sped up only 41-fold in DMSO relative to decalin.
Impurities are likely to consist of either pyrrolidine or alpha-dibrominated alkylphenones—respectively, from either excess pyrrolidine or incomplete amination during synthesis. These impurities likely account for its discoloration and fishy (pyrrolidine) or bromine-like odor, which worsens upon exposure to air, moisture, or bases. [8]
Ring-opening polymerization can proceed via radical, anionic, or cationic polymerization as described below. [19] Additionally, radical ROP is useful in producing polymers with functional groups incorporated in the backbone chain that cannot otherwise be synthesized via conventional chain-growth polymerization of vinyl monomers.