931-64-6

Basic information

• Product Name: 2,2,2-BICYCLO-2-OCTENE
• Synonyms: 2,2,2-BICYCLO-2-OCTENE;BICYCLO(2.2.2)-2-OCTENE;2,2,2-Bicyclooctene-2;3,6-Endoethylenecyclohexene;Bicyclo[2.2.2]octene;Cyclohexene, 3,6-endo-(1,2-ethanediyl)-;BICYCLO[2.2.2]OCT-2-ENE;Bicyclo[2.2.2]octa-5-ene
• CAS NO: 931-64-6
• Molecular Formula: C₈H₁₂
• Molecular Weight: 108.18
• Mol File: 931-64-6.mol
• Article Data: 13

Chemical Properties

• Melting Point: 111.4°C
• Boiling Point: 137.85°C (rough estimate)
• Flash Point: 18.5 °C
• Appearance: /
• Density: 0.8341 (estimate)
• Vapor Pressure: 8.41mmHg at 25°C
• Refractive Index: 1.4770 (estimate)
• CAS DataBase Reference: 2,2,2-BICYCLO-2-OCTENE(CAS DataBase Reference)
• NIST Chemistry Reference: 2,2,2-BICYCLO-2-OCTENE(931-64-6)
• EPA Substance Registry System: 2,2,2-BICYCLO-2-OCTENE(931-64-6)

Safety Data

• Hazardous Substances Data: 931-64-6(Hazardous Substances Data)

Usage

General Description

2,2,2-Bicyclo-2-octene is a bicyclic organic compound with the molecular formula C10H16. It consists of two fused cyclohexane rings with a double bond between carbons 1 and 2. This colorless liquid is used as a starting material for the synthesis of various organic compounds, including pharmaceuticals and agrochemicals. It is also utilized as a solvent in organic reactions and as a flavoring agent in the food industry. 2,2,2-Bicyclo-2-octene is flammable and should be handled with care due to its potential health hazards.

InChI:InChI=1/C8H12/c1-2-8-5-3-7(1)4-6-8/h1-2,7-8H,3-6H2

Synthetic route

Bicyclo[2.2.2]octanon-(2)-p-toluolsulfonylhydrazonn (94064-42-3) → norbornene (931-64-6)

Conditions	Yield
With N,N,N,N,-tetramethylethylenediamine; methyllithium	99%
With N,N,N,N,-tetramethylethylenediamine; methyllithium In diethyl ether cooling;	99 % Chromat.

endo-bicyclo<2.2.2>oct-5-en-2-ol mesylate → norbornene (931-64-6)

Conditions	Yield
With lithium triethylborohydride In tetrahydrofuran at 60℃; for 4h;	83%

5-(phenylsulfonyl)bicyclo<2.2.2>oct-2-ene (77550-13-1) → norbornene (931-64-6)

Conditions	Yield
With disodium hydrogenphosphate; sodium amalgam In tetrahydrofuran; methanol for 3.5h;	78.5%
With sodium amalgam; Na2HPO4 buffer In methanol at -20℃;	78%

Bicyclo<2.2.2>octane-2,3-di-exo-carboxylic anhydride (7131-66-0) → norbornene (931-64-6)

Conditions	Yield
With lead dioxide at 250℃;

acetic acid bicyclo[2.2.2]oct-2-yl ester (51677-42-0) → norbornene (931-64-6)

Conditions	Yield
at 400℃;

bicyclo[2.2.2]oct-5-en-2-one (2220-40-8) → norbornene (931-64-6)

Conditions	Yield
With hydrazine hydrate anschliessend Erhitzen mit Kaliumhydroxid und Diaethylenglykol auf 220grad;

ethene (74-85-1) + cyclohexa-1,3-diene (1165952-91-9) → norbornene (931-64-6)

Conditions	Yield
at 250℃;
at 280℃;

ethene (74-85-1) + cyclohexa-1,3-diene (1165952-91-9) + hydroquinone (123-31-9) → norbornene (931-64-6)

Conditions	Yield
at 250℃; under 58840.6 Torr;

1-phenyl-3-(bicyclo<2.2.2>octan-2-yl)triazene (90893-09-7) → norbornene (931-64-6) + exo-bicyclo<3.2.1>octan-2-yl acetate (51744-61-7, 51744-62-8, 92015-56-0, 135094-46-1, 145166-92-3) + tricyclo<3.2.1.02,7>octane (285-43-8) + bicyclo<2.2.2>oct-2-yl-acetate (51677-42-0) + N-(endo-bicyclo<3.2.1>)oct-2-yl-aniline (93638-25-6, 93638-27-8)

Conditions	Yield
With sodium acetate; acetic acid Product distribution; Mechanism; deamination reactions of amine via triazene;

ethyl N-nitroso-N-(bicyclo<3.2.1>octan-2-yl)carbamate (90893-13-3) → norbornene (931-64-6) + Bicyclo<3.2.1>oct-2-ene (823-02-9, 61617-43-4, 84235-38-1) + N-(bicyclo<2.2.2>octyl)aniline (93638-23-4) + tricyclo<3.2.1.02,7>octane (285-43-8) + (1R,3R,5S)-Bicyclo[3.2.1]oct-3-yl-phenyl-amine (93638-31-4) + N-(exo-bicyclo<3.2.1>oct-2-yl)aniline (93638-25-6, 93638-27-8)

Conditions	Yield
With ethanol Product distribution; Mechanism; deamination reactions of amine via nitrosocarbamate;

S-p-tolyl-S-vinyl-N-(p-tolylsulfonyl)sulfoximine (89279-63-0) + cyclohexa-1,3-diene (1165952-91-9) → norbornene (931-64-6)

Conditions	Yield
With disodium hydrogenphosphate; sodium amalgam 1.) CHCl3, 110 deg C, 50 h 2.) r.t., 75 min; Yield given. Multistep reaction;

ethyl N-nitroso-N-(exo-bicyclo<3.2.1>octan-2-yl)carbamate (90893-12-2, 90893-14-4) → norbornene (931-64-6) + Bicyclo<3.2.1>oct-2-ene (823-02-9, 61617-43-4, 84235-38-1) + N-(bicyclo<2.2.2>octyl)aniline (93638-23-4) + tricyclo<3.2.1.02,7>octane (285-43-8) + (1S,3S,5R)-Bicyclo[3.2.1]oct-3-yl-phenyl-amine (93638-29-0) + N-(exo-bicyclo<3.2.1>oct-2-yl)aniline (93638-25-6, 93638-27-8)

Conditions	Yield
With ethanol Product distribution; Mechanism; deamination reactions of amine via nitrosocarbamate;

3-(Trimethylsilyl)bicyclo<2.2.2>octan-2-carbonsaeure → norbornene (931-64-6)

Conditions	Yield
With potassium hydroxide In ethanol; acetonitrile Ambient temperature; electrolysis: C-anode, Pt-catode;	74 % Chromat.

trans-2,3-diiodobicyclo<2.2.2>octane → norbornene (931-64-6)

Conditions	Yield
With methyl iodide In gas at 100℃;

Bicyclo<2.2.2>octane-2,3-di-exo-carboxylic anhydride (7131-66-0) + lead (IV)-oxide → norbornene (931-64-6)

Conditions	Yield
at 250℃;

(+-)-2-trimethylammonio-bicyclo<2.2.2>octane hydroxide → norbornene (931-64-6) + (+-)-2-dimethylamino-bicyclo<2.2.2>octane

Conditions	Yield
With potassium hydroxide

2-methylenebicyclo[2.2.1]heptane (497-35-8, 139683-15-1) + phosphoric acid /kieselguhr → norbornene (931-64-6) + cis-1,2,3,3a,4,6a-hexahydro-pentalene + substances of high boiling point

Conditions	Yield
at 250℃;

bicyclo[2.2.2]octan-2-one (2716-23-6) → norbornene (931-64-6) + tricyclo<3.2.1.0.2.7>octane (285-43-8)

Conditions	Yield
With pyrographite at -196.15℃;

2,2-dibromo-bicyclo[2.2.2]octane → norbornene (931-64-6) + tricyclo<3.2.1.0.2.7>octane (285-43-8)

Conditions	Yield
With methyllithium at 65℃;

C15H20N2O2S → norbornene (931-64-6) + tricyclo<3.2.1.0.2.7>octane (285-43-8)

Conditions	Yield
at 25℃; Photolysis;

bicyclo[4.2.0]oct-2-ene (13367-29-8) → norbornene (931-64-6)

Conditions	Yield
at 300℃; Kinetics;

bicyclo[4.2.0]oct-2-ene (13367-29-8, 22567-94-8, 56029-14-2) → ethene (74-85-1) + norbornene (931-64-6) + cyclohexa-1,3-diene (1165952-91-9)

Conditions	Yield
at 275℃; Kinetics; Further Variations:; Temperatures;

bicyclo[2.2.2]octan-2-one (2716-23-6) → norbornene (931-64-6)

Conditions	Yield
Multi-step reaction with 2 steps 1: 0.99 g / methanol 2: 99 percent Chromat. / MeLi; TMEDA / diethyl ether / cooling View Scheme
Multi-step reaction with 2 steps 1: 68 percent / methanol 2: 99 percent / MeLi; TMEDA View Scheme

bicyclo[2.2.2]oct-5-en-2-one (68908-13-4, 2220-40-8, 16196-15-9, 68069-67-0) → norbornene (931-64-6)

Conditions	Yield
Multi-step reaction with 3 steps 1: H2 / Pd/C / ethanol / 2 h 2: 0.99 g / methanol 3: 99 percent Chromat. / MeLi; TMEDA / diethyl ether / cooling View Scheme

cyclohexa-1,3-diene (1165952-91-9) → norbornene (931-64-6)

Conditions	Yield
Multi-step reaction with 5 steps 1: 6.9 g / hydroquinone / 90 - 100 °C 2: KOH / dimethylsulfoxide; H2O / 20 h 3: H2 / Pd/C / ethanol / 2 h 4: 0.99 g / methanol 5: 99 percent Chromat. / MeLi; TMEDA / diethyl ether / cooling View Scheme
Multi-step reaction with 4 steps 1.2: 17 percent / KOH / H2O; dimethylsulfoxide 2.1: 89 percent / H2 / Pd/C 3.1: 68 percent / methanol 4.1: 99 percent / MeLi; TMEDA View Scheme

2-chlorobicyclo<2.2.2>oct-5-ene-2-carbonitrile → norbornene (931-64-6)

Conditions	Yield
Multi-step reaction with 4 steps 1: KOH / dimethylsulfoxide; H2O / 20 h 2: H2 / Pd/C / ethanol / 2 h 3: 0.99 g / methanol 4: 99 percent Chromat. / MeLi; TMEDA / diethyl ether / cooling View Scheme

(1S,4S)-(-)-bicyclo<2.2.2>oct-5-en-2-one (68069-67-0) → norbornene (931-64-6)

Conditions	Yield
Multi-step reaction with 3 steps 1: 89 percent / H2 / Pd/C 2: 68 percent / methanol 3: 99 percent / MeLi; TMEDA View Scheme

5-hydroxybicyclo[2.2.2]oct-2-ene (6688-07-9, 19245-72-8, 55320-40-6, 68069-65-8, 68069-66-9, 70981-36-1, 74958-54-6, 123001-31-0) → norbornene (931-64-6)

Conditions	Yield
Multi-step reaction with 2 steps 1: pyridine 2: 83 percent / LiBEt3H / tetrahydrofuran / 4 h / 60 °C View Scheme

cyclohexa-1,3-diene (1165952-91-9) + (methoxyphenylcarbene)molybdenum complex (22) → norbornene (931-64-6)

Conditions	Yield
Multi-step reaction with 3 steps 1: 2.) aq. NaOH, aq. H2O2 / 1.) room temp., 1 h, 2.) THF, 1 h, 50 deg C 2: pyridine 3: 83 percent / LiBEt3H / tetrahydrofuran / 4 h / 60 °C View Scheme

norbornene (931-64-6) → 3H-benzo-1,2-dithiole (272-21-9) + 3,4,5-Trithia-tricyclo[5.2.2.02,6]undecane (130094-83-6, 130147-95-4)

Conditions	Yield
With BPTC In dimethyl sulfoxide at 150℃; for 12h;	A 97% B 98%

norbornene (931-64-6) → bicyclo[2,2,2]octane (280-33-1)

Conditions	Yield
With hydrogen; palladium on activated charcoal In hexane at 20 - 22℃;	97%
With magnesium; palladium on activated charcoal In methanol Ambient temperature;	96%
With hydrazine hydrate In ethanol for 24h; Reflux;	42%

norbornene (931-64-6) + (E)-1-iodo-3,3-dimethyl-1-butene (61382-45-4) → (R)-2-((E)-3,3-Dimethyl-but-1-enyl)-bicyclo[2.2.2]octane

Conditions	Yield
With tetrabutyl-ammonium chloride; potassium formate; palladium diacetate In N,N-dimethyl-formamide at 25℃; for 24h;	96%

norbornene (931-64-6) + α,α-diphenylbenzenemethanesulfenyl chloride (35572-83-9) → endo-2-chloro-exo-1-(triphenylmethyldithio)bicyclo<2.2.2>octane

Conditions	Yield
In dichloromethane for 20h; Ambient temperature;	87%

norbornene (931-64-6) + thiophenol (108-98-5) → 3-(phenylthio)bicyclo[2.2.2]octane (92865-78-6)

Conditions	Yield
at 75 - 80℃; for 0.5h;	85.6%

norbornene (931-64-6) → (S)-Bicyclo[2.2.2]oct-2-yl-trichloro-silane (145964-29-0)

Conditions	Yield
With trichlorosilane; (Ra)-(2'-methoxy-[1,1']-binaphthalenyl-2-yl)-diphenylphosphine; bis(η3-allyl-μ-chloropalladium(II)) at 0℃; for 24h;	85%

2-iodobenzonitrile (4387-36-4) + norbornene (931-64-6) → C15H16O

Conditions	Yield
With palladium diacetate; tetrabutyl-ammonium chloride; triethylamine In N,N-dimethyl-formamide at 100℃; for 48h;	82%

cis-bis(acetonitrile)chloronitropalladium(II) (91547-45-4) + norbornene (931-64-6) → [Pd(N(O)OCH(CH(CH2CH2)2CH)CH)Cl]2 (91443-53-7)

Conditions	Yield
In acetone under N2, alkene added to soln. of Pd complex in acetone, reacted for 5-10 min; ppt. sepd., washed with acetone, dried overnight in vac.;	80%

[Ir(hydrido)2(acetone)2(triphenylphosphine)2](BF4) (82582-67-0, 72414-17-6) + norbornene (931-64-6) → Ir(C8H10){(C6H5)3P}2(1+)*BF4(1-) (79792-66-8)

Conditions	Yield
In dichloromethane reflux, 4h, under N2; the cooled soln. was reduced to 5 mL in vac. and Et2O was added until a solid had pptd., recrystn. from CH2Cl2/Et2O, elem. anal.;	78%

norbornene (931-64-6) → trans-2,3-dibromobicyclo<2.2.2>octane (72444-00-9, 90085-73-7, 130985-93-2)

Conditions	Yield
With bromine In pyridine; chloroform at -40℃;	72.3%

norbornene (931-64-6) → bicyclo[2.2.2]octan-2-ol (18684-63-4)

Conditions	Yield
With dimethylsulfide borane complex; dihydrogen peroxide In diethyl ether	70%
With sodium tetrahydroborate; boron trifluoride diethyl etherate In diethylene glycol dimethyl ether

norbornene (931-64-6) + tritylsulfenyl chloride (24165-03-5) → endo-2-chloro-exo-1-(triphenylmethyldithio)bicyclo<2.2.2>octane

Conditions	Yield
Ambient temperature;	65%
In dichloromethane for 20h; Ambient temperature;	43%

diazomethane (186581-53-3, 908094-01-9) + norbornene (931-64-6) → tricyclo<3.2.2.02,4>nonane (278-80-8)

Conditions	Yield
palladium(II) acetylacetonate In diethyl ether at -10℃;	64%

norbornene (931-64-6) + potassium cyanide (151-50-8) + tert-Butyl-[(S)-1-((Z)-2-iodo-vinyl)-hexyloxy]-dimethyl-silane (143168-90-5) → 3-[(E)-(S)-3-(tert-Butyl-dimethyl-silanyloxy)-oct-1-enyl]-bicyclo[2.2.2]octane-2-carbonitrile (143088-08-8)

Conditions	Yield
palladium diacetate; triphenylphosphine In N,N-dimethyl-formamide at 80℃;	63%

ortho-methylphenyl iodide (615-37-2) + norbornene (931-64-6) → 5-methyl-1,2,3,4,4a,8b-hexahydro-1,4-cis,exo-ethanobiphenylene

Conditions	Yield
With tetrakis(triphenylphosphine) palladium(0); potassium carbonate In N,N-dimethyl-formamide at 105℃; for 24h;	62%

norbornene (931-64-6) + 9,10-phenanthrenequinone (84-11-7) → C22H20O2 (76036-59-4)

Conditions	Yield
In benzene for 40h; Irradiation;	53%

2-Iodophenol (533-58-4) + norbornene (931-64-6) → 1,4-ethano-1,2,3,4,4a,9b-hexahydrodibenzofuran

Conditions	Yield
With palladium diacetate; tetrabutylammomium bromide; potassium carbonate In N,N-dimethyl-formamide at 80℃; for 24h;	52%

norbornene (931-64-6) → bicyclo<2.2.2>octane-cis-2,3-diol (33746-54-2)

Conditions	Yield
With potassium permanganate; sodium hydroxide In methanol; water; toluene at 5℃;	46%
With potassium permanganate; acetone
With pyridine; osmium(VIII) oxide; diethyl ether Behandeln des Reaktionsprodukts mit Mannit und wss. KOH in CH2Cl2;

2-Iodothiophene (3437-95-4) + norbornene (931-64-6) → (S)-2-Bicyclo[2.2.2]oct-2-yl-thiophene

Conditions	Yield
With tetrabutyl-ammonium chloride; potassium formate; palladium diacetate In N,N-dimethyl-formamide at 25℃; for 24h;	39%

iodobenzene (591-50-4) + norbornene (931-64-6) → 1,2,3,4,4a,8b-hexahydro-5-phenyl-1,4-ethanobiphenylene + 1,2,3,4,4a,12b-hexahydro-8-phenyl-1,4-ethanotriphenylene + 1,2,3,4,4a,8b-hexahydro-5-<2'-(3'-phenyl)bicyclo<2.2.2>octyl>-1,4-ethanobiphenylene

Conditions	Yield
With tetrakis(triphenylphosphine) palladium(0); potassium carbonate In N,N-dimethyl-formamide at 80℃; for 24h;	A 18% B 34% C 21%

norbornene (931-64-6) → 3,4,5-Trithia-tricyclo[5.2.2.02,6]undecane (130094-83-6, 130147-95-4)

Conditions	Yield
With S2	15%

tert-butyl (2E,4Z)-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)penta-2,4-dienoate (888965-55-7) + norbornene (931-64-6) → (Z)-(2S,3R,4R)-4-Tricyclo[3.2.2.02,4]non-3-yl-but-3-enoic acid tert-butyl ester

Conditions	Yield
With potassium fluoride; chloro(1,5-cyclooctadiene)rhodium(I) dimer; tri tert-butylphosphoniumtetrafluoroborate In 1,4-dioxane; water at 80℃; for 3h;	15%
With potassium fluoride; chloro(1,5-cyclooctadiene)rhodium(I) dimer; tri tert-butylphosphoniumtetrafluoroborate In 1,4-dioxane; water at 80℃; for 3h; Inert atmosphere;	15%

norbornene (931-64-6) → cis-cyclohexane-1,4-dicarboxylic acid (619-81-8)

Conditions	Yield
With dihydrogen peroxide In methanol; formic acid; water; ethyl acetate	13%
With dihydrogen peroxide In methanol; formic acid; water; ethyl acetate	13%
With dihydrogen peroxide In methanol; formic acid; water; ethyl acetate	13%
Multi-step reaction with 2 steps 1: (i) aq. H2O2, HCO2H, Et2O, (ii) LiAlH4 2: CrO3, aq. H2SO4 / acetone View Scheme

norbornene (931-64-6) + naphthalene-2,6-diamine (2243-67-6) + 2,6-bis(1-methylethyl)benzaldehyde → C52H58N2

Conditions	Yield
Stage #1: norbornene; naphthalene-2,6-diamine; 2,6-bis(1-methylethyl)benzaldehyde With boron trifluoride diethyl etherate In dichloromethane for 80h; Reflux; Stage #2: With manganese(IV) oxide In 1,2-dichloro-benzene for 16h; Reflux;	9%

diisopropyl xanthogen disulfide (105-65-7) + norbornene (931-64-6) → exo-3,5-dithiatricyclo<6.2.1.02,6>undecan-4-one

Conditions	Yield
With 2,2'-azobis(isobutyronitrile) In benzene for 12h; Heating;	3%

Allyl acetate (591-87-7) + norbornene (931-64-6) → 2-methylene-3-vinyl-bicyclo[2.2.2]octane

Conditions	Yield
tetrakis(triphenylphosphine) palladium(0) In acetonitrile at 80℃; Cycloaddition;	3%

Upstream product

• 74-85-1 ethene 
• 1165952-91-9 cyclohexa-1,3-diene 
• 123-31-9 hydroquinone 
• 89279-63-0 S-p-tolyl-S-vinyl-N-(p-tolylsulfonyl)sulfoximine 
• 7131-66-0 Bicyclo<2.2.2>octane-2,3-di-exo-carboxylic anhydride 
• 497-35-8 2-methylenebicyclo[2.2.1]heptane 
• 38259-00-6 bicyclo<2.2.2>oct-5-ene-2-carboxaldehyde 
• 107-13-1 acrylonitrile 
• 89015-36-1 endo-3-(Trimethylsilyl)bicyclo<2.2.2>oct-5-en-exo-2-carbonsaeure 
• 6688-07-9 5-hydroxybicyclo[2.2.2]oct-2-ene 
• 68069-67-0 (1S,4S)-(-)-bicyclo<2.2.2>oct-5-en-2-one 
• 68908-13-4 bicyclo[2.2.2]oct-5-en-2-one 
• 2716-23-6 bicyclo[2.2.2]octan-2-one 
• 13367-29-8 bicyclo[4.2.0]oct-2-ene 

Downstream Products

• 278-84-2 2,3-epoxybicyclo<2.2.2>oct-2-ene 
• 280-33-1 bicyclo[2,2,2]octane 
• 33649-79-5 2-chloro-bicyclo[2.2.2]octane 
• 930-99-4 (3aS,6aS)-1,2,3,3a,4,6a-Hexahydro-pentalene 
• 4802-43-1 exo-bicyclo<3.2.1>oct-3-en-2-ol 
• 10474-95-0 endo-8-Brom-bicyclo<3.2.1>octen-(2) 
• 278-80-8 tricyclo<3.2.2.0^2,4>nonane 
• 40335-86-2 (S)-(+)-bicyclo[2.2.2]octan-2-ol 
• 37165-30-3 (-)-Bicyclo<2.2.1>octan-2-ol 
• 33746-54-2 trans dihydroxy-2,3 bicyclo<2.2.2>octane 
• 18684-63-4 bicyclo[2.2.2]octan-2-ol 
• 619-81-8 cis-cyclohexane-1,4-dicarboxylic acid 
• 704204-47-7 (1R,2R,5R)-Bicyclo[3.2.1]oct-2-ylamine 
• 5019-82-9 bicyclo[3.2.1]octan-2-one 

Relevant articles and documents

Unsaturated aldehydes as alkene equivalents in the Diels-Alder reaction

A one-pot procedure is described for using α,β-unsaturated aldehydes as olefin equivalents in the Diels-Alder reaction. The method combines the normal electron demand cycloaddition with aldehyde dienophiles and the rhodium-catalyzed decarbonylation of aldehydes to afford cyclohexenes with no electron-with-drawing substituents. In this way, the aldehyde group serves as a traceless control element to direct the cycloaddition reaction. The Diels-Alder reactions are performed in a diglyme solution in the presence of a catalytic amount of boron trifluoride etherate. Subsequent quenching of the Lewis acid, addition of 0.3% of [Rh(dppp)2Cl] and heating to reflux achieves the ensuing decarbonylation to afford the product cyclohexenes. Under these conditions, acrolein, crotonaldehyde and cinnamaldehyde have been reacted with a variety of 1,3-dienes to afford cyclohexenes in overall yields between 53 and 88%. In these transformations, the three aldehydes serve as equivalents of ethylene, propylene and styrene, respectively.

Thermal reactions of 7-d- and 8-d-bicyclo[4.2.0]oct-2-enes

The gas phase thermal reactions exhibited by bicyclo[4.2.0]oct-2-ene and 7-d and 8-d analogues at 300 °C have been followed kinetically through GC and 2H NMR spectroscopic analyses. In contrast to the pattern of transformations exhibited by bicyclo[3.2.0]hept-2-ene and deuterium-labeled analogues, no reactions initiated by C1-C6 bond cleavage are seen, epimerization at C8 is much faster than [1,3] shifts leading to bicyclo[2.2.2]oct-2-ene, and the ratio of rate constants for [1,3] carbon migration with inversion versus migration with retention is ～1.4. Homolysis of C1-C8 to give a conformationally flexible diradical intermediate having a relatively long lifetime and multiple options for further reaction (re-formation of C1-C8 with or without net epimerization, fragmentation to 1,3-cyclohexadiene and ethylene, migration to the original C3 with inversion or retention) accords well with the observations. Clearly, orbital symmetry control does not govern stereochemistry for the [1,3] sigmatropic carbon shifts. Copyright