(3+3)‐Annulation of Donor–Acceptor Cyclopropanes with Diaziridines

Abstract

The first example of (3+ +3)-annulation of two different three-membered rings is reported herein. Donoracceptor cyclopropanes in reaction with diaziridines were found to affordp erhydropyridazine derivatives in high yields and diastereoselectivity under mild Lewis acid catalysis.T he disclosed reaction is applicable for the broad substrate scope and exhibits an excellent functional group tolerance.

Synthesis of 1‐Substituted Pyrazolines by Reaction of Donor‐Acceptor Cyclopropanes with 1,5‐Diazabicyclo[3.1.0]hexanes

“…A similar yield of pyrazolines 4d was obtained in the reaction of 6‐ethyl‐6‐methyl analogue 2e and monosubstituted 6‐ethyl derivative 2f . The latter was highly unexpected as earlier both 6‐aryl‐1,5‐diazabicyclo[3.1.0]hexanes and 1,2,3‐triethyldiaziridine in the reaction with D–A cyclopropanes produced only products of (3+3)‐annulation . Oppositely, 6,6‐dimethyl‐substituted diazabicyclohexane 2g afforded pyrazoline 4d in 18 % yield only; the major product of its reaction with 1d was (3+3)‐cycloadduct 3a .…”

“…Cyclopropane 1c with electron‐depleted 4‐fluorophenyl substituent afforded pyrazoline 4c in 46 % yield only. This tendency can be explained by Lewis acid‐induced side reactions of 2a such as its dimerization, and partial decomposition; the contribution of side reactions increases with the decrease of D–A cyclopropane reactivity.…”

“…The reaction of D–A cyclopropanes 1 with a series of 1,5‐diazabicyclo[3.1.0]hexanes 2 . a) (3+3)‐Annulation of two three‐membered rings affording hexahydropyridazine derivatives 3 . b) 2,3‐Dihydro‐1 H ‐pyrazolines 4 formation (this work).…”

“…Very recently, we have described the reaction of donor‐acceptor (D–A) cyclopropanes, 1 with bicyclic diaziridines 2 affording hexahydropyridazines 3 as a first example of (3+3)‐annulation of two different three‐membered rings (Scheme a) . However, under the same conditions spiro[cyclohexane‐1,6′‐(1,5‐diazabicyclo[3.1.0]hexane)] 2a did not produce the corresponding hexahydropyridazine affording other product.…”

(3+3)‐Annulation of Carbonyl Ylides with Donor–Acceptor Cyclopropanes: Synergistic Dirhodium(II) and Lewis Acid Catalysis

“…[1] Besides alkenes and alkynes,w hich are the most prominent systems to undergo cycloaddition reactions,d onor-acceptor (D-A) cyclopropanes have in numerous cases been successfully involved in such transformations.T heir use as 1,3zwitterionic synthons is promoted by their high strain energy and by the polarized bond between the carbon atoms bearing the donor and the acceptor moiety.After seminal work in this field by Wenkert and Reissig some 30 to 40 years ago,the field has vastly expanded, especially during the last decade,leading to novel protocols of rearrangements,c ycloadditions,a nd ring-opening reactions. Most of the (1,n)dipoles that have been inserted are stable compounds (aldehydes, [4] imines, [5] allenes, [6] thiocarbonyls, [7] azides, [8] nitrones, [9] diaziridines;S cheme 1A [10] )o rc an be generated by the stoichiometric addition of base from astable precursor (such as nitrile imines;S cheme 1B). Most of the (1,n)dipoles that have been inserted are stable compounds (aldehydes, [4] imines, [5] allenes, [6] thiocarbonyls, [7] azides, [8] nitrones, [9] diaziridines;S cheme 1A [10] )o rc an be generated by the stoichiometric addition of base from astable precursor (such as nitrile imines;S cheme 1B).…”