102870-46-2Relevant academic research and scientific papers
Norpinenes (Bicyclohept-2-enes) from Homobenzvalenes (Tricyclo2,7>hept-3-enes)
Herzog, Clemens,Lang, Reinhard,Brueckner, Dieter,Kemmer, Petra,Christl, Manfred
, p. 3027 - 3044 (2007/10/02)
4,5-Dibromo-(1b) and 4,5-dichlorohomobenzvalene (1c) were converted into the tetrahalonorpinenes 2b, c by elemental bromine.In the case of unsubstituted homobenzvalene (1a) the analogous reaction could be achieved in 1percent yield only by pyridinium perbromide.Treatment of 1a, b as well as of chlorohomobenzvalenyl nitrobenzoate 1d with iodine furnished the diiodonorpinenes 3a - c.However, 7,7-dibromotetracyclo2,4.03,5>heptane (4) and bromine gave the tetrabromo-trans-tricyclo2,4>heptane derivative 5. - On irradiation in the presence of thiophenol, the homobenzvalenes 1a, c, e, f were transformed into the 6-(phenylthio)norpinenes 6a - d.The hydroxyhomobenzvalenes 1g, h afforded the 6-(phenylthio)norpinenes 6e, g as major products, the configuration at C-4 of which is inverted as compared to that of 6b - d.By using 2>-1a it was shown that with respect to stereochemistry the addition of thiophenol does not proceed uniformly.Without irradiation, 1a was consumed by thiophenol rather slowly at 20 deg C with formation of the norcarene derivatives 9 and 10 in addition to 6a. - By treatment with LiAlH4 the dichloro compound 6b gave the monochloro derivative 6h.Both 6b and 6h, however the latter one with a better yield, were converted into unsubstituted norpinene (11a) by means of sodium in liquid ammonia, thus providing a new and preparatively useful synthesis for 11a.Analogously, 6c, d furnished 4-phenylnorpinene (11b).The reaction of norpinenes 3a and 11a with N-bromosuccinimide produced the allylbromides 3d and 11c, respectively. - 13C NMR spectra of the 4-substituted norpinenes revealed a diagnostically important γ-anti-substituent effect.
