1-methoxycyclohepta-1,3,5-triene

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: subsequently isomerizing said 3-methoxycycloheptatriene by acid catalyzed rearrangement with methanolic hydrogen chloride followed by neutralization to give a crude 1-methoxycycloheptatriene product and

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: The preferred embodiment of the improved process of this invention involves the use of the above mentioned process modifications of the prior art process, particularly the use of the polymerization inhibitor phenothiazine, with the additional process improvement of heating the 7-methoxycycloheptatriene in the second step of the process to an elevated temperature, e.g., 180° C. at reduced pressure to give a final product 1-methoxycycloheptatriene of increased mole percent yield and purity. More specifically, it has been found that when 7-methoxycycloheptatriene is heated at 180° C. under reduced pressure, a substantial quantity of the order of 80 mole % of 7-isomer is isomerized to 1-methoxycycloheptatriene with complete consumption of the 7-isomer whereas heating at 150° C. (atmosphere pressure), as in the prior art process, yields the 3-methoxycycloheptatriene as a major component with only approximately 12-13 mole % 1-methoxycycloheptatriene product. Subsequent acid catalyzed rearrangement (step 3 of the synthesis) of the product in the preferred process yields a final product containing approximately 92 mole % of the 1-methoxy isomer and a purity of methoxy isomers of 99 mole % versus a yield of 90 mole % 1-methoxy isomer (96% purity of methoxy isomer) obtained when the improved process of this invention utilizes the atmospheric heating at 150° C. of the prior art process.

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: An improved multi-step process for synthesizing the liquid irritant 1-methoxycycloheptatriene through the steps of reacting cycloheptatrienyl tetrafluoroborate in aqueous solution with methanol and sodium bicarbonate to produce 7-methoxycycloheptatriene, thermally isomerizing the 7-methoxycycloheptatriene to 3-methoxycycloheptatriene by heating at 150° C. for 2 hours and isomerizing the 3-methoxycycloheptatriene to 1-methoxycycloheptatriene by acid, catalyzed rearrangement employing methanolic hydrogen chloride followed by neutralization with sodium bicarbonate, filtration and fractional distillation to give the final product the improvement comprising the step of utilizing a polymerization/condensation inhibitor to increase the overall yield and purity of the 1-methoxycycloheptatriene product. The overall yield and purity of the product can further be increased through the step of conducting the thermal isomerization of 7-methoxy to 3- and 1-methoxycycloheptatriene at 180° C. under reduced pressure, e.g., by heating in a sealed reactor.

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: In the first step of the above synthesis, warm water is used to dissolve the cycloheptatrienyl tetrafluoborate (tropylium tetrafluoborate) (I) salt under a nitrogen atmosphere. Methanol is added to the resulting aqueous solution of (I), followed by the addition of solid sodium bicarbonate to give the reaction product 7-methoxycycloheptatriene (II). The 7-methoxycycloheptatriene (II) is isomerized by heating at 150° C. for two hours to produce 3-methoxycycloheptatriene (III). In the third step, 3-methoxycycloheptatriene (III) is isomerized in an acid catalyzed rearrangement utilizing hydrogen chloride in methanol at room temperature for two hours, followed by neutralization with sodium bicarbonate, filtration and fractional distillation to give the product 1-methoxycycloheptatriene (IV). at room temperature for two hours followed by neutralization with sodium bicarbonate, filtration and fractional distillation