Synthesis and Physical Properties of Sterically Congested Cycloalkenes, 1,2-Di-tert-butyl-3,3,5,5-tetramethylcyclopentene and 1,2-Di-tert-butyl-3,3,6,6-tetramethylcyclohexene

Abstract

Two sterically congested cycloalkenes (9 and 10), congeners of tetra-tert-butylethylene, were synthesized and characterized. Oxidation of the bicyclic 1,3-dithietane 8 with dimethyldioxirane (DMD) gave the endo,endo-disulfoxide 13, thermal isomerization of which to the endo,exo-disulfoxide 15 followed by oxidation with DMD gave the trioxide 18. Heating 18 in refluxing 1,3-dimethyl-2-imidazolidinone furnished 1,2-di-tert-butyl-3,3,5,5-tetramethylcyclopentene (9) in 69% yield by a 2-fold extrusion process. The reaction of the 1,6-diketone dihydrazone 23 with Se(2)Cl(2) gave the selenadiazoline 34 and the 1,3-diselenetane 35. Heating 34 at 115-130 degrees C gave 1,2-di-tert-butyl-3,3,6,6-tetramethylcyclohexene (10), a "didehydro" derivative of tetra-tert-butylethylene, in 43% yield. The C=C bond in 10 is strained in degree comparable to those of most strained alkenes reported so far.

Reactions of sterically congested 1,6‐ and 1,7‐bis(diazo)alkanes with elemental sulfur and selenium: Formation of cyclohexene, 1,2‐dithiocane, 1,2‐diselenocane, and 1,2,3‐triselenecane derivatives

“…1,6-Bis(diazo)hexane 5 was prepared from the corresponding dihydrazone 3 [1] by oxidation with nickel peroxide (NiPO) [8]. Compound 5 was heated with an excess amount of elemental selenium (5 molar amounts) in DBU at 130…”

“…• C for 30 min, 1,3,4-selenadiazoline 2 [1] was isolated in 61% yield. This strongly suggests that 1, obtained in the reaction at 130…”

“…To a solution of 2,2,4,4,7,7,9,9-octamethyldecane-3, 8-dione dihydrazone (3) [1] (302 mg, 0.971 mmol) in ether (40 ml) was added nickel peroxide [8] (4.10 mmol g −1 , 595 mg, 2.44 mmol), and the mixture was stirred for 2 h at room temperature. The insoluble materials were removed by filtration, and the filtrate was dried and evaporated to dryness to give the 1,6-bis(diazo)hexane 5 (288 mg, 96%) as orange crystals.…”

“…Recently we reported the synthesis of a sterically congested cyclohexene 1 [1] by a twofold extru- sion process [2] of the 1,3,4-selenadiazoline 2 which was prepared by the reaction of dihydrazone 3 with Se 2 Cl 2 (Scheme 1). The formation of 2 was explained by an intramolecular cyclization of diazoselenoketone 4 [1,3].…”

“…The formation of 2 was explained by an intramolecular cyclization of diazoselenoketone 4 [1,3]. In our continuous study on the chemistry of sterically congested cycloalkenes, we examined the reaction of bis(diazo)alkanes 5 and 6 with elemental sulfur and selenium in expectation of the formation of 1 and a cycloheptene derivative 7, respectively.…”