SEQUENTIAL CYCLOADDITION-CYCLOREVERSION-CYCLOADDITION-COPE REARRANGEMENT WITH AN ANNELATED NORBORNADIENE AND ELECTROPHILIC DIENES - UNUSUAL [PI(2)(S)+PI(2)(A)+SIGMA(2)(A)] TRANSFORMATION OF A PENTACYCLO-[11.4.0.1(7,10).0(4,13).0(6,11)]OCTADECA-3,8,14,17-TETRAENE

TY - JOUR

T1 - SEQUENTIAL CYCLOADDITION-CYCLOREVERSION-CYCLOADDITION-COPE REARRANGEMENT WITH AN ANNELATED NORBORNADIENE AND ELECTROPHILIC DIENES - UNUSUAL [PI(2)(S)+PI(2)(A)+SIGMA(2)(A)] TRANSFORMATION OF A PENTACYCLO-[11.4.0.1(7,10).0(4,13).0(6,11)]OCTADECA-3,8,14,17-TETRAENE

AU - GRAVETT, E C

AU - HOWARD, J A K

AU - MACKENZIE, K

AU - LIU, S X

AU - KARADAKOV, P B

PY - 1993/5/21

Y1 - 1993/5/21

N2 - Hexachloronorbornadiene efficiently forms a 1:1 adduct 3 with 5,6-bismethylenenorbornene. Adduct 3 on reaction with 1,2,3,4-tetrachlorothiophene dioxide (TCTD) under mild conditions gives an SO2 bridged adduct, which loses SO2, the product cycloreverting to give 1,2,3,4-tetrachlorobenzene and an annelated cyclopentadiene 8; 8 reacts further with TCTD to give, in 1:1 ratio, two compounds (14 and 15) shown by mass, C-13 and H-1 NMR spectroscopy and single crystal X-ray structure determination to be the stereoisomeric products of a rare type of specific diene capture by TCTD. Evidence is presented that this result (and analogous examples) is best understood in terms of ''normal'' [4+2]pi cycloadditions to 8 as dienophile towards electron-deficient TCTD, followed by rapid Cope rearrangement of the SO2-bridged intermediate adducts to give the observed products. At low temperatures adduct 3 behaves as expected towards electron-deficient diene tetracyclone ; the [4+2]pi cycloadduct decarbonylates on mild thermolysis, concomitant cycloreversion also giving diene 8. At much higher temperatures in the presence of excess tetracyclone, diene 8 likewise behaves as dienophile; the carbonyl-bridged major cycloadduct decarbonylates to give an intermediate which undergoes an unusual thermally-allowed [pi2s + pi2a + sigma2a] 1,3-shift/cycloaddition, delivering a symmetrical cage-like structure 24, as indicated by mass and C-13 and H-1 NMR spectroscopy.

AB - Hexachloronorbornadiene efficiently forms a 1:1 adduct 3 with 5,6-bismethylenenorbornene. Adduct 3 on reaction with 1,2,3,4-tetrachlorothiophene dioxide (TCTD) under mild conditions gives an SO2 bridged adduct, which loses SO2, the product cycloreverting to give 1,2,3,4-tetrachlorobenzene and an annelated cyclopentadiene 8; 8 reacts further with TCTD to give, in 1:1 ratio, two compounds (14 and 15) shown by mass, C-13 and H-1 NMR spectroscopy and single crystal X-ray structure determination to be the stereoisomeric products of a rare type of specific diene capture by TCTD. Evidence is presented that this result (and analogous examples) is best understood in terms of ''normal'' [4+2]pi cycloadditions to 8 as dienophile towards electron-deficient TCTD, followed by rapid Cope rearrangement of the SO2-bridged intermediate adducts to give the observed products. At low temperatures adduct 3 behaves as expected towards electron-deficient diene tetracyclone ; the [4+2]pi cycloadduct decarbonylates on mild thermolysis, concomitant cycloreversion also giving diene 8. At much higher temperatures in the presence of excess tetracyclone, diene 8 likewise behaves as dienophile; the carbonyl-bridged major cycloadduct decarbonylates to give an intermediate which undergoes an unusual thermally-allowed [pi2s + pi2a + sigma2a] 1,3-shift/cycloaddition, delivering a symmetrical cage-like structure 24, as indicated by mass and C-13 and H-1 NMR spectroscopy.

KW - DIELS-ALDER REACTION

KW - CYCLO-ADDITIONS

KW - DOUBLE-BOND

KW - THIOPHENE

KW - STEREOSELECTIVITY

KW - DERIVATIVES

KW - PARALLEL

KW - MNDOC

M3 - Article

SN - 0040-4020

VL - 49

SP - 4699

EP - 4710

JO - Tetrahedron

JF - Tetrahedron

IS - 21

ER -