Addition von Dihalocarbenen an bicyclische Olefine; Herstellung von Bicyclo[3.2.1]octan- undexo-Tricyclo[4.2.1.0^2,4]nonan-Derivaten^1,2

Synthesis of Functionalized Bicyclo[3.2.1]octanes and Their Multiple Uses in Organic Chemistry

“…267 This tandem addition-ring expansion is efficient with norbonenes 463 or norbornadiene 268 and has been used quite often as a simple and inexpensive preparative method for the construction of useful functionalized bicyclo[3.2.1]octanes. Spontaneous rearrangement of cyclopropyl intermediates 464 gives the corresponding dihalo bicyclic olefins 465 which can be selectively manipulated to give either lactone 466, bicyclooctanones 467 or 201, tricyclo[4.2 × 10 2,4 ]nonane 468 269 or vinyl halides 469 270 (Scheme 7). The latter (X ) Br) has been used to prove the transient existence of the highly strained bicyclic allene 470 trapped as either enol ether 471 or as its styrene [2+2] cycloadduct 472.…”

Vinyl chloride as a masked carbonyl group: An experimental project for advanced students

“…The starting compound 3-chlorobicyclo[3.2.1]oct-2-ene, 1, is prepared from commercially available norbornene (bicyclo[2.2.1]hept-2-ene) by a two-step synthesis (4), in good yield; norbornene is first transformed into exo-3,4-dichlorobicyclo[3.2.1]oct-2-ene by means of an interesting phasetransfer catalysis (yield 74%). It is then reduced by LiAlH4 into compound 1 (yield 86%).…”

“…This coupling is made possible because of a s-cis conformation between the carbinolic proton H2 and the hydroxylic proton OH around the C-O bond, in agreement with the observed c/h-0-C2-H2 value (8). Two other doublets at 4.55 ppm (broad, =;5%) and 4.15 ppm (neat, JH-0-Cr H[ = 4 Hz, 8%) are respectively assigned to hydroxylic protons in isomers 4c (endo OH) and 4b (exo OH). All these signals disappear with addition of CF3COOH into the solution.…”

Phase-Transfer Catalysis Reaction with Strong Bases

“…Though not fully explained, it is clear from preliminary results of asymmetric dichlorocarbene addition to styrene using the 2-hydroxyethyl catalyst that some specific interaction of the hydroxy group of the quaternary ammonium cation is occurring. Mechanistic studies have been performed for the addition of dichloroand dibromocarbene to norbomadiene [228,229],43, and norbomene, 44 [230]. The reaction of five-membered heterocycles with dichlorocarbene yields six-membered heterocycles (and minor amounts of addition products; selectivity is discussed below).…”