83205-20-3Relevant academic research and scientific papers
6-Substituted Bicyclohept-5-en-2-one Ketals
Lal, Kasturi,Salomon, Robert G.
, p. 2628 - 2632 (2007/10/02)
Structurally specific syntheses of isomerically pure 6-substituted bicyclohept-5-en-2-one ketals were explored.A conversion of the Diels-Alder adduct of itaconic anhydride with cyclopenta-1,3-diene into a ketal of 6-methylbicyclohept-5-en-2-one was accomplished, but the last step, an oxidative vicinal bisdecarboxylation, gave only a 35percent yield.The ethylene ketal of 6-methylbicyclohept-5-en-2-one was prepared in 80percent overall yield from bicyclohept-5-en-2-one by a regioselective replacement of hydrogen with a methyl group.Practical synthesesof the 6-bromo, 6-carbomethoxy, 6-phenylthio, and 6-trimethylsilyl analogues were accomplished similarly.
112. The Carbonyl Group as Homoconjugated Electron-Releasing Substituent. Regioselective Electrophilic Additions at Bicyclohept-5-en-2-one, Bicyclooct-5-en-2-one, and Derivatives
Carrupt, Pierre-Alain,Vogel, Pierre
, p. 1008 - 1028 (2007/10/02)
In CHCl3, CH3CN, or AcOH, benzeneselenenyl chloride (PhSeCl), bromide (PhSeBr), and acetate (PhSeOAc), 2-nitrobenzenesulfenyl chloride (NO2C6H4SCl), and 2,4-dinitrobenzenesulfenyl chloride ((NO2)2C6H3SCl) added to bicyclohept-5-en-2-one (5) in an anti fashion with complete stereo- and regioselectivity, giving adducts 20-24 in which the chloride, bromide, or acetoxy substituent (X) occupies the endo position at C(6) and the Se- or S-substituent (E) the exo position at C(5).The addition 5+(NO2)2C6H3SCl->24 was accompanied by the formation of (1RS,2RS)-2-(2,4-dinitrophenylthio)cyclopent-3-ene-1-acetic acid (25).The latter was the major product in AcOH containing LiClO4.The addition of PhSeCl and PhSeBr to bicyclooct-5-en-2-one (6) were less stereoselective (proportion of exo vs. endo mode of electrophilic attack was ca. 3:1) but highly regioselective giving adducts 27/28 and 29/30, respectively, the regioselectivity being the same as that of the electrophilic addition of 5.The reaction of PhSeCl with a 4:1 mixture of 2-exo-chloro- and 2-endo-chlorobicyclohept-5-ene-2-carbonitriles (12) was slower then addition 5+PhSeCl; it gave adducts 31/32 (4:1) in which the PhSe moiety occupies the exo position at C(6) and the Cl atom the endo position at C(5).The addition of PhSeCl to 2-chlorobicyclooct-5-ene-2-carbonitriles (13) was very slow and gave adducts with the same regioselectivity as 12+PhSeCl, but opposite with that of reactions of the corresponding enones 5 and 6.PhSeX (X=Cl, Br, OAc) added to 2-cyanobicyclohept-5-en-2-yl acetates (14) with the same regioselectivity as 12+PhSeCl.The addition of PhSeCl, PhSeBr, NO2C6H4SCl, and (NO2)2C6H3SCl to 2-(bicyclohept-5-en-2-ylidene)propanedinitrile (49) were not regioselective, showing that a dicyanomethylidene function is not like a carbonyl function when homoconjugated with a ? system.The results are in agreement with predictions based on MO calculations suggesting that a carbonyl group homoconjugated with an electron-deficient centre can behave as an electron-donating, remote substituent because of favourable n(CO)?C(1),C(2)p(C(6)) hyperconjugative interaction.
REGIOSELECTIVE ADDITIONS OF ELECTROPHILES TO OLEFINS REMOTELY PERTURBED. THE CARBONYL GROUP AS A HOMOCONJUGATED ELECTRON DONATING SUBSTITUENT.
Carrupt, Pierre-Alain,Vogel, Pierre
, p. 2563 - 2566 (2007/10/02)
Electrophiles attack preferentially at the C(5) position of 2-norborn-5-enone and 2-bicyclooct-5-enone whereas the C(6) position is preferred for 2-chloronorborn-5-ene-2-carbonitriles and 2-chlorobicyclooct-5-ene-2-carbonitriles.
