Preparation of Isopropylidenebenzocyclobutenes <i>via</i> the Photochemical Cyclization of 1-(<i>o</i>-Alkylaryl)-3-hydroxy-2,2-dimethyl- alkan-1-ones

Yoshioka, Michikazu; Iida, Kei; Kawata, Etsuya; Maeda, K.; Kumakura, Shigekazu; Hasegawa, Tadashi

doi:10.1021/jo962167+

Cited by 4 publications

(9 citation statements)

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“…The 2,2-dimethylbenzocyclobutenols 3a and 3b were prepared from the isopropylidenebenzocyclobutene 1. 8 Epoxidation of 1 with m-CPBA followed by oxidative cleavage of the resulting epoxide with periodic acid gave the 2,2-dimethylbenzocyclobutenone 2. 9 The reaction of 2 with methylmagnesium iodide and ethylmagnesium bromide gave 3a and 3b, respectively (Scheme 1).…”

Section: Resultsmentioning

confidence: 99%

“…8 The configurations of other 2,2-dimethylbenzocyclobutenols 6 and 7 were deduced by comparison of their chromatographic behavior with those of 6a and 7a. 8 Thermal Reaction of 1-Alkyl-2,2-dimethylbenzocyclobutenols. When 1-methyl (3a) and 1-ethyl (3b) substituted 2,2-dimethylbenzocyclobutenols were heated at 160 °C for 4 h in a glass tube, they were converted into the 2-isopropenylphenyl alcohol 8a,b and the 2-isopropylphenyl ketone 9a,b in a ratio given in Table 1.…”

Section: Resultsmentioning

confidence: 99%

“…Preparation of 2,2-Dimethylbenzocyclobutenols. The 2,2-dimethylbenzocyclobutenols 3a and 3b were prepared from the isopropylidenebenzocyclobutene 1 .…”

Section: Resultsmentioning

confidence: 99%

“…Methods for the preparation of the diastereomeric 2,2-dimethylbenzocyclobutenols 6a-e and 7a-e and their physical properties have already been described in a previous paper. 8 Preparation of 4-Isopropyl-2,2-dimethylbenzocyclobuten-1(2H)-one (2). To a solution of 1-isopropylidene-4isopropyl-2,2-dimethyl-1,2-dihydrobenzocyclobutene (1) 8 (360 mg 1.68 mmol) in CH2Cl2 (20 mL) was added a solution of m-CPBA (337 mg (1.95 mmol) in CH2Cl2 (10 mL) at room temperature.…”

Section: Methodsmentioning

confidence: 99%

“…8 Preparation of 4-Isopropyl-2,2-dimethylbenzocyclobuten-1(2H)-one (2). To a solution of 1-isopropylidene-4isopropyl-2,2-dimethyl-1,2-dihydrobenzocyclobutene (1) 8 (360 mg 1.68 mmol) in CH2Cl2 (20 mL) was added a solution of m-CPBA (337 mg (1.95 mmol) in CH2Cl2 (10 mL) at room temperature. After 30 min of stirring at room temperature, a solution of periodic acid (350 mg, 1.53 mmol) in THF (10 mL) was added.…”

Section: Methodsmentioning

confidence: 99%

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Stereospecific Thermal Isomerization of 2,2-Dimethylbenzocyclobutenols to 2-Isopropenylphenyl Alcohols

2000

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Thermolysis of the 1-alkyl-2,2-dimethylbenzocyclobutenol 3 at 160 degrees C gave the 2-isopropenylphenyl alcohol 8 through an (E)-dienol intermediate by a 1,5-sigmatropic hydrogen shift from the isopropylidene methyl group to the carbon bearing hydroxy group. In the thermolysis of each of the diastereomeric 2, 2-dimethylbenzocyclobutenols 6 and 7 which have a hydroxy group on the beta-carbon of the quaternary C(1)-alkyl substituent, the isomerization to the 2-isopropenylphenyl alcohols 10 and 11 took place stereospecifically through a twisted (E)-dienol intermediate. The configuration of the newly formed chiral center in 10 and 11 was the same as that of the ring carbon bearing hydroxy group in the starting 6 and 7.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

“…Preparation of 2,2-Dimethylbenzocyclobutenols. The 2,2-dimethylbenzocyclobutenols 3a and 3b were prepared from the isopropylidenebenzocyclobutene 1 .…”

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

See 3 more Smart Citations