Synthesis and anomalous structure–reactivity relationship of 8,11-dichloro[5]metacyclophan-3-one

On the mechanism of a new dihalocyclopropane‐dihalomethyl vinyl rearrangement

“…The most plausible reaction mechanism consistent with our findings was, however, the one observed from the deconjugated vinylcyclopropane cyclohexanes [23]. In this case, the biradical structure (Scheme 4b in one step or two steps) either -cleaves the C-C bond of cyclopropane as by the Makosza pathway, or -cleaves one of two C-CX 2 bonds, leading to our rearrangement compound.…”

“…Spontaneous and forced cleavages and rearrangements of the cyclopropane ring are an even more important question in the field of biologically-important products, because of the presence of an extensive family of gem-dihalocyclopropane derivatives currently available from the addition of carbenes to the double bonds and their hydrolysis to cyclopropanones. The direct result of this addition, the dihalocyclopropane ring, is much more susceptible to chemicallyinduced modifications, proceeding generally through carbocationic or radical mechanisms, internal nucleophilic substitution (often metal-assisted), and photochemical or microwave-assisted transformations [11][12][13][14][15][16][17][18][19][20][21][22][23]. As a result, a new class of biological products, metabolites, and intermediates has been created.…”

“…We conclude that a two-oxidation-state Lewis-acid reagent is necessary to perform the rearrangement reaction, in order to obtain either the allene Hiyama analogue or the dihalomethyl vinyl compound. The concurrent Lewis-acid-assisted pathway (Scheme 3) leads to the stable alpha halovinyl cation [20][21][22][23], for which, however, the formation of specific addition or hydrolysis products was not observed. As already mentioned, the presence of the hydride anion is necessary to maintain the Cr +2 formation.…”

Selected synthetic strategies to cyclophanes

“…Double elimination reaction: In 2001, Bickelhaupt and co-workers [ 232 ] have synthesized a [5]metacyclophane derivative with an sp 2 -center embedded at the central position of the bridge. Ditosylate 459 was converted to dibromide 460 by treatment with LiBr followed by the addition of dichlorocarbene to give the cyclopropane derivative 461 according to the Skattebøl method [ 233 ].…”

p -Toluenesulfonylmethyl Isocyanide: a Versatile Synthon in Organic Chemistry

“…Dichlorocarbene addition to 316 gave 317 which was cyclized with TosMIC to give propellane 318. Cyclophanone 319 was prepared from 318 by double HCl elimination with AgClO 4 and lutidine in THF (Scheme 115)[99].…”