Site selectivity in the addition of ketoximes to activated allenes and alkynes; N- versus O-alkylation

Abstract

Reaction of ketoximes with methyl propiolate afforded geometrical isomers of the methyl 3-(hydroxyimino)-propanoates 4 and of the O-vinyl oximes 5 as well as the 2-isoxazoline 6. With dimethyl penta-2,3-diendioate 8c reaction progressed via an O-alkylation to give the O-oxime ethers 9, only in the case of cyclopentanone oxime was the spirocyclic dihydroazepinol 11 also obtained, its identity has been confirmed by an X-ray structure determination.

High diastereoselectivity induced by intermolecular hydrogen bonding in [3 + 2] cycloaddition reaction: experimental and computational mechanistic approaches

“…Endo‐E transition state is another possible transition state on the reaction route to the cis ‐diastereomer (Figure ). The secondary orbital interactions , noncovalent attractive interactions between the N ‐bonded aromatic rings belonging to the E‐ nitrone and the maleimide can cause the reaction to proceed via this transition state . There are large numbers of studies that support cycloaddition reactions via E ‐nitrones .…”

Synthesis of Some Novel Bisisoxazolidine Derivatives from Glyoxal‐derived Bisnitrones via Simultaneous Double Cycloaddition Reactions in Water

“…Bisnitrones ( 1 ) reacted with N ‐substituted maleimides giving bisisoxazolidines. Diastereoselective reactions of the dipole 1 furnished diastereoselective cycloadducts ( 2 , 3 , 4 ) and are classified as trans biscycloadducts as the 3‐H and 4‐H protons on each isoxazolidine ring are trans orientated as evidenced from 1 H‐NMR spectroscopy . On the other hand, bisnitrones 1 reacted with ethyl acrylate and styrene giving exclusively regioselective bisisoxazolidines ( 5 , 6 ).…”

Synthesis of isomeric 2,3,5‐trisubstituted perhydropyrrolo[3,4‐d]‐isoxazole‐4,6‐diones via 1,3‐dipolar cycloaddition reactions

“…Then, column chromatography of the residue ( n ‐hexane/ethyl acetate 1:1) gave nitrone (compound 2). The crude product was recrystallized from CH 2 Cl 2 / n ‐hexane [45].…”