The photochemistry of five 11-hydroxy-1,5-cyclopregn-3-en-2-ones (‘lumi’ products from the corresponding pregna-1,4-dien-3- ones) has been investigated. In all cases the photoproducts were 1,11-oxy derivatives, resulting from intramolecular attack of the hydroxyl group to the incipient positive charge at C-1. When a fluorine atom was present at C-6, HF elimination took place concurrently with the nucleophilic addition and led to linearly conjugated dienones, rather than the enones obtained in the other cases. Quantum yields were in the range 0.06–0.2, the lower values applying when a fluorine atom was present in position 6 (not in position 9). The results add new evidence on the role of zwitterionic intermediates in the photochemistry of cross-conjugated dienones and the corresponding lumi photoproducts.
Photochemistry of some steroidal bicyclo[3.1.0]hexenones
RICCI, ANDREA;FASANI, ELISA;MELLA, MARIELLA;ALBINI, ANGELO
2004-01-01
Abstract
The photochemistry of five 11-hydroxy-1,5-cyclopregn-3-en-2-ones (‘lumi’ products from the corresponding pregna-1,4-dien-3- ones) has been investigated. In all cases the photoproducts were 1,11-oxy derivatives, resulting from intramolecular attack of the hydroxyl group to the incipient positive charge at C-1. When a fluorine atom was present at C-6, HF elimination took place concurrently with the nucleophilic addition and led to linearly conjugated dienones, rather than the enones obtained in the other cases. Quantum yields were in the range 0.06–0.2, the lower values applying when a fluorine atom was present in position 6 (not in position 9). The results add new evidence on the role of zwitterionic intermediates in the photochemistry of cross-conjugated dienones and the corresponding lumi photoproducts.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
