Synthese und Struktur adamantylsubstituierter Methylenaziridine1)

Synthesis and applications of methyleneaziridines

Methyleneaziridines (MAs) are a special subset of aziridines featuring an exocyclic C–C double bond on the three-membered ring. They have found great potential in organic synthesis. In this review, the structural characterization of MAs, synthetic methods, chemical transformations and mechanisms, especially the advances achieved over the past decade are comprehensively summarized.

This review surveys the structural characterization, synthetic methods, chemical transformations and mechanisms of methyleneaziridines, especially the advances achieved over the past decade.

Solid-phase, multicomponent reactions of methyleneaziridines: synthesis of 1,3-disubstituted propanones

[reaction: see text] Polymer-supported methyleneaziridines undergo ring opening by Grignard reagents under copper catalysis to yield metalloenamines which are alkylated in situ to yield ketimines. Filtration and washing of these Merrifield resin-bound intermediates prior to hydrolysis provides the corresponding 1,3-disubstituted propanones in a high state of purity without recourse to column chromatography.

New Synthesis of Propargylic Amines from 2-(Bromomethyl)aziridines. Intermediacy of 3-Bromoazetidinium Salts

A new, efficient, and straightforward synthesis provides propargylamines in high overall yields (64-77%) by transformation of 1-(arylmethyl)-2-(bromomethyl)aziridines into N,N-di(arylmethyl)-N-(2-propynyl)amines via N-(2,3-dibromopropyl)amines and N-(2-bromo-2-propenyl)amines. The conversion of N-(2,3-dibromopropyl)amines into N-(2-bromo-2-propenyl)amines is based on a novel analogue of the Hofmann elimination. A Yamaguchi-Hirao alkylation, a Sonogashira coupling, or a hydroarylation reaction further functionalized these propargylamines toward potentially interesting compounds for medicinal and agrochemical use.

Multicomponent reactions involving 2-methyleneaziridines: rapid synthesis of 1,3-disubstituted propanones

Ring opening of 1-alkyl-2-methyleneaziridines 1 or 2 is accomplished with organocopper reagents (R(2)CuLi or RMgX/CuI) in the presence of boron trifluoride diethyl etherate giving 1-substituted propan-2-ones 3-9 in 42-88% yield. Ring opening with RMgCl/CuI in the absence of the Lewis acid allows further alkylation of the metalloenamine (metalated imine) intermediate in a regiocontrolled manner. The sequential formation of two new intermolecular carbon-carbon bonds in this reaction provides a rapid entry into a variety of 1,3-disubstituted propan-2-ones, including 11 and 14-23. The scope and mechanism of this multicomponent reaction (MCR) has been assessed. It is established that this MCR tolerates alkyl, aryl, and benzylic Grignard reagents and a wide range of electrophiles, including alkyl iodides, bromides, and tosylates, as well as epoxides and aldehydes. In addition, gem-dimethyl substitution on the exocyclic double bond of the 2-methyleneaziridine is tolerated. This MCR has been applied to the one-pot synthesis of (Z)-6-heneicosen-11-one, 25, an important sex attractant of the Tussock moth. Using 3-deuterio-1-(1-phenylethyl)-2-methyleneaziridine, 26, we determined that this MCR occurs predominantly by direct ring opening at the sp(3)-hybridized aziridine carbon atom (C-3).