Synthesen in der hydroaromatischen Reihe. I. Die Kondensation von Methyl‐cyclopenten‐dion mit Butadien

Dane, Elisabeth; Schmitt, Joseph; Rautenstrauch, Curt

doi:10.1002/jlac.19375320103

Cited by 13 publications

(4 citation statements)

References 2 publications

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“…1 H NMR spectra were recorded at 200, 250, 270, and 400 MHz; chemical shifts (δ) are given in ppm, and J in Hz. The diene 2 , the diketone 5 , and the reference substances rac - 8 and rac - 9 10 were prepared according to published methods.…”

Section: Methodsmentioning

confidence: 99%

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Catalysis of a Diels−Alder Reaction by Amidinium Ions

2000

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Amidines and guanidines are important functional groups in molecular recognition and host-guest chemistry. Here it is shown that lipophilic amidinium ions catalyze a cycloaddition reaction representing the key step of the Quinkert-Dane estrone synthesis. Hydrogen-bond-mediated association with the organic cation leads to an electrophilic activation of the dienophile and to enhanced rates of the Diels-Alder reaction. The observed effects are similar to those expected from mild Lewis acids. In competition experiments, amidinium catalysis favors the reaction of the less electron deficient dienophile.

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Section: Methodsmentioning

confidence: 99%

“…The first reaction constitutes a simple case in which rac - 3 is formed from maleic anhydride 1 and diene 2 (Scheme ) . A more complex behavior is observed in the cycloaddition of 2 and diketone 5 . This reaction leads to rac - 8 , a key intermediate in the Quinkert−Dane synthesis of estrone (Scheme ) …”

Section: Introductionmentioning

confidence: 99%

Catalysis of a Diels−Alder Reaction by Amidinium Ions

2000

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“…6-Methoxy-l-vinyl-3,4-dihydronaphthalene (1) reacted also with cyclic ketones already containing a methyl group; frequently two products were obtained, as was the case of 2-methyl-l-cyelopentene-3,4-dione, with the 14-methyl isomer (10) predominating [6][7][8][9][10]. Attempts to reverse this mode of addition have been largly unsuccessful until recently.…”

Section: Carbocyclicsmentioning

confidence: 99%