Alkenylation, aziridine

Alkenyl aziridines, for C—N bonds via amination, 10, 704 ( 7-l-Alkenylboronates, synthesis, 9, 154 1-Alkenylboronates, synthesis, 9, 168... 

Gini, F. Del Moro, F. Macchia, F. Pineschi, M. Regio- and enantioselective Cu-catalyzed addition of dialkylzinc reagents to cyclic 2-alkenyl aziridines. Tetrahedron Lett. 2003,... 

For the aziridination of 1,3-dienes, copper catalysis gave better yields of A-tosyl-2-alkenyl aziridines with 1,3-cyclooctadiene, 1,4-addition occurred exclusively (50%) [46]. Good results were also obtained on rhodium catalysed decomposition of PhI=NNs (Ns = p-nitrophenylsulphonyl) with some alkenes the aziridination was stereospecific, whereas with chiral catalysts asymmetric induction (up to 73% ee) was achieved. However, cyclohexene gave predominantly (70%) a product derived from nitrene insertion into an allylic carbon-hydrogen bond [47]. 

Alkenyl aziridines are useful synthetic building blocks and can be converted to allylamines by conjugate addition of organocuprates [29], to pyrroline derivatives by rearrangement [30] and to P-lactams by Pd-catalyzed carbonylation [31]. 

Ring-Opening Cyclization of 2-(3-Alkenyl)aziridines and 3-(3-Alkenyl)oxaziridines... 

Iska, V.B.R., Gais, H.-J., Tiwari, S.K. er a/. (2007) Asymmetric aziridination with chiral allyl aminosulfonium ylides synthesis of alkenyl aziridine carboxyaltes and palladium-catalysed E, trans/ , cis-isomerization of an alkenyl aziridine. Tetrahedron Letters, 48, 7102-7107. 

Aziridines with Nitrogen Unsubstituted 3J2.2 N-Alkyl- and N-Alkenyl-aziridines... 

Chaabouni et al., who treated the quaternized hydrazones (240) with vinyl-magnesium bromide and obtained the product (241) of both cyclization and alkylation in excellent yield. The resulting alkenyl aziridines were hydroborated, halogenated, and cyclized to the fused aziridinoazacycles (242) as shown in Scheme 33. The cyclization proceeded in yields of 40—70% save in the case of n = 2 from which the product (243) was presumably too unstable to be isolated. 

V-Alkenyl aziridines 14 can be accessed through Pd(0)-mediated reaction of aziridines 12 with alkenyl halides 13. A wide variety of Al-alkenyl aziridines 14, containing many substituents, alkyl, aryl, ester, ketone, etc., may be synthesized in good yields (eq 14). 

Dalili S, Yudin AK (2005) Transition metal-catalyzed synthesis and reactivity of n-alkenyl aziridines. Org Lett 7 1161-1164... 

Siebert MR, Yudin AK, Tantillo DJ (2008) Cycloaddition/Ring opening reaction sequences of n-alkenyl aziridines influence of the aziridine nitrogen on stereoselectivity. Org Lett 10 57-60... 

A variety of nitrogen nucleophiles have been utilized in Pd-catalyzed 77-alkenylation reactions. For example, Bolm has employed iV-alkenylation reactions for the preparation of iV-alkenyl sulfoximines (Eq. 18) [140], and Yudin has applied this method to the synthesis of W-alkenyl aziridines (Eq. 19) [141]. Analogous W-arylation reactions of sulfoximines and aziridines have also been developed [142, 143]. Movassaghi has effected W-alkenylation reactions between functionalized alkenyl triflates and several aromatic nitrogen heterocycles including indoles and pyrroles (Eq. 20) [144]. The use of p-chloroacrolein derivatives as substrates in iV-alkenylation reactions has also been illustrated [145, 146]. 

Yudin and co-workers used aziridines as the amino partner in palladium-catalyzed alkenylations with vinyl halides developing thus a straightforward method for the synthesis of N-alkenyl aziridines (Scheme 19) [75]. They observed that copper catalysts provided comparatively lower 5delds, albeit allowed for the preparation of some aziridines inaccessible with a palladium catalyst. Due to the sensitivity of the coupling products toward aziridine ring opening on silica gel, the crude reactions had to be purified by either distillation or flash chromatography on alumina to ensure acceptable yields. 

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