[3 + 3]-Cycloaddition of Donor–Acceptor Cyclopropanes with Nitrile Imines Generated in Situ: Access to Tetrahydropyridazines

Abstract

Donor-acceptor cyclopropanes are reacted under the influence of a Lewis acid with hydrazonyl chlorides to afford tetrahydropyridazines. Formally, this transformation can be regarded as a [3 + 3]-cycloaddition of three-membered rings and nitrile imines generated in situ. This efficient method provides fast access to a variety of structurally diverse pyridazine derivatives. The structure of a typical product was confirmed by X-ray crystallography.

Intriguing Electrophilic Reactivity of Donor–Acceptor Cyclopropanes: Experimental and Theoretical Studies

“…The presence of both antagonist partners on adjacent carbon atoms (C1 and C2) combined with the inherent ring strain of the cyclopropane (about 27.5 kcal mol –1 ) provide a C1–C2 bond prone to heterolytic cleavage, and ring opening can therefore occur under mild conditions (usually under heating or Lewis acid activation). A valuable 1,3‐dipole synthetic building block is thus delivered (Scheme , left) and has been utilized in plethora of reactions, for instance: nucleophilic trapping, [3+2], [3+3], and [3+4] cycloaddition reactions as well as rearrangement . Some of the resulting molecules have been used as advanced materials in the construction of biologically relevant targets ,.…”

Visible‐Light Photocatalytic Intramolecular Cyclopropane Ring Expansion

“…Therefore, in the presence of a Lewis acid, 1,3‐zwitterions can be generated and trapped by different double bonds, that is C=C, C=N, C=O. Brilliant examples of intermolecular cycloadditions (Scheme a) from the groups of Maulide, Trushkov, Tang, Doyle, Tomilov, and Werz– have been reported recently, while the group of Wang and others have developed related intramolecular cross‐cycloadditions (IMCC; Scheme b)…”

Donor–Acceptor Cyclopropanes as an Expedient Building Block Towards the Construction of Nitrogen‐Containing Molecules: An Update

“…reported for the first time a [3+3] cycloaddition reaction of DACs 3 with hydrazonyl chlorides 112 to afford tetrahydropyridazines 113 . Hydrazonyl chlorides 112 generated nitrile imines on treatment with imidazole, which then react with various DACs 3 in the presence of a catalytic amount of TiCl 4 to yield the desired pyridazine derivatives 113 in good yield (up to 92%) (Scheme ) . The reaction conditions are well tolerated by both electron‐donating and electron‐withdrawing substituents on the aromatic rings of DACs and nitrile imines.…”