Reactions of the zwitterions from trisubstituted electron-deficient ethylenes and electron-rich olefins

Cyclization and annulation reactions of nitrogen-substituted cyclopropanes and cyclobutanes

“…From that a short four-step sequence (reduction, acylation, hydrogenation and silyl deprotection) without any purification of the intermediate products gave goniomitine (44) in 18% overall yield for 13 steps. 19 Preliminary investigations seemed to indicate a sub-micromolar cytotoxicity, but more in depth investigations showed later no significant bioactivity.…”

“…Indeed, product 40 was shown to be more stable by 6.6 kcal/mol by calculation. 20b The possibility to obtain the N-cyclization product was highly interesting, because the formed tetracylic system constitutes the core of another alkaloid natural product, goniomitine (44), which had been much less studied than aspidosperimidine (30). 21 In fact, the N-cyclization of aminocyclopropane 42, obtained from the bis-lithiated intermediate derived from indole 41 onto Weinreb amide 38, was obtained in 93% yield.…”

“…42 In particular, the first examples of efficient annulation reactions involving DA cyclobutanes have been reported. 43 However, even if the ring opening of aminocyclobutanes has been known since a long time, 44 there was only one example of [4+2] annulation between DA aminocyclobutane and carbonyl compounds reported by Saigo and co-workers prior to 2013 (eqn 16). 43a In this transformation, the obtained half aminals were unstable and directly hydrolysed.…”

Synthesis and Reactivity of Donor-Acceptor Substituted Aminocyclopropanes and Aminocyclobutanes

“…In the case of a thermal process, the concerted cycloaddition path is forbidden and therefore harsh conditions are required to cross the activation barrier [185][186][187][188][189]. Uncatalyzed methods employing thermal activation have been hampered by the requirement of strongly reactive partners and therefore were limited to enamines and electron poor olefins such as tricyanoethylene.…”

Synthesis of novel β-aminocyclobutanecarboxylic acid derivatives by a solvent-free aza–Michael addition and subsequent ring closure

“…29,30,31,32 β-Aminocyclobutanedicarboxylic acid derivatives are a poorly studied class of donor-acceptor (DA) substituted cyclobutanes which are prone to ring opening reactions. 33,34 Therefore, in this work, the use of 3-halopropylidenemalonate derivatives as substrates for the synthesis of new β-aminocyclobutanedicarboxylic acid derivatives via an aza-MIRC reaction was investigated.…”