Hypervalent-iodine(iii) oxidation of hydrazones to diazo compounds and one-pot nickel(ii)-catalyzed cyclopropanation

Abstract

A novel and efficient cyclopropanation protocol that can be applicable to general hydrazones and alkenes with broad functionalities.

Surface modification of polymers with bis(arylcarbene)s from bis(aryldiazomethane)s: preparation, dyeing and characterization

“…It is worth noting that bis(aryldiazomethane)s 3d~e contain unprotected amino groups, but they are very stable in the oxidation step with manganese dioxide as oxidant. These oxidation conditions are very mild, allowing selective oxidation of the hydrazone to the diazo compound [28][29][30] , which leaves free amine undamaged. The greater stability of these systems compared to the diazo compound derived from Michler's ketone is noteworthy 22 .…”

Non-stabilized diazoalkane synthesis via the oxidation of free hydrazones by iodosylbenzene and application in in situ MIRC cyclopropanation

“…We deemed that iodosylbenzene would be the perfect oxidizing reagent as its reduction would only generate one equivalent of the benign iodobenzene and water as byproducts (Scheme 1b). The group of Cai reported the successful oxidation of the benzophenone-derived hydrazone with this reagent for the development of a one-pot nickel( ii )-catalyzed cyclopropanation 16. While this hydrazone is known to be stable and the corresponding semi-stabilized diazo compound is known to be more resilient, mono- and bis-alkyl hydrazones are prone to decompose into azines under the reaction conditions.…”

Cyclopropanation Reactions of Semi-stabilized and Non-stabilized Diazo Compounds

“…59 To solve this, Cai et al developed an in situ generation of diphenyldiazomethanes and subsequent nickel(II) catalyzed cyclopropanations of olefins using the simple iodosylbenzene as oxidizing agent. 60 Moderate to excellent yields were obtained with short reaction times (Scheme 17). The use of arylalkyl hydrazones was also explored, giving the desired compounds in moderate to good yields, albeit with low diastereoselectivities (Scheme 17).…”

“…91 As previously described in this review, iodosylbenzene has been used by Cai et al for the oxidation of benzophenone-derived hydrazones, with its reduction only generating one equivalent of iodobenzene and water as byproducts. 60 By using this benign organic oxidant, we recently developed an easy and efficient access to a broad range of non-stabilized diazoalkanes and their subsequent in situ MIRC cyclopropanations under batch conditions for the first time. 92 The slow addition of a solution of a free hydrazone onto a suspension of the oxidant and the desired Michael acceptor in ethyl acetate allowed the degradation of the starting material in the reaction mixture to be prevented.…”