Novel Cyclization Reactions of Aminoallenes

Abstract

The aminoallene moiety represents an excellent building block for heterocyclization reactions, affording a large number of cyclic structures containing different sized skeletons in a single step. This strategy has been studied under basic and electrophile-induced conditions. More recently, the use of transition metal catalysis has been introduced as an alternative relying on the activation of the allenic component. This overview focuses on the most recently developed cyclizations of aminoallenes along with remarkable early works accounting for the mechanism, as well as for the regio-and stereoselectivity of the cyclizations.

Synthesis of (−)‐Deoxynupharidine by Allenic Hydroxylamine Cyclisation

“…[8,9] We subsequently applied this methodt ot he synthesis of nupharamine 1,a nd the unnamed indolizidine Nuphar alkaloid 3,b oth in racemic form. [10] We now report the application of this method to the synthesis of deoxynupharidine 2, [11] aq uinolizidine Nuphar alkaloid, in enantioenriched form.T he synthesis of all three alkaloids proceeds via the diene 4 as ac ommon intermediate by cross-metathesis with different partners( Scheme 1).…”

Copper Hydride-Catalyzed Enantioselective Synthesis of Axially Chiral 1,3-Disubstituted Allenes

“…Additionally, enantioenriched allenyl alcohols and amines are known to serve as valuable synthetic intermediates toward the production of chiral heterocycles including dihydrofurans and dihydropyrroles. 3h, 34,35 Taking advantage of the highly selective nature of gold-catalyzed cycloisomerization chemistry, α-aminoallene 4l furnished 2,5-dihydropyrrole 6 with complete axial-to-point chirality transfer (Scheme 2b). 36,37 In summary, we have developed a LCuH-catalyzed asymmetric semireduction of 1,3-enynes to supply highly enantioenriched 1,3-disubstituted allenes in up to 98% yield and >99:1 er.…”

Recent Advances in the Construction of Polycyclic Compounds by Palladium‐Catalyzed Atom‐Economical Cascade Reactions

“…[33] It is well-known that arylpalladium halides, themselves generated in situ from aryl halides and palladium(0), regioselectively react with allenes to form p-allylpalladium(II) intermediates, such as 91 (Scheme 20). [34] Combined with alkene carbopalladation (91 to 92) and sequential direct arylation/ C À H bond functionalization (92 to 90), the tricyclic isoindole derivatives 90 were produced from allenenes 89. It is noteworthy that this reaction does not require a tetrasubstituted carbon atom for suppression of b-hydride elimination.…”