Two reaction pathways were elaborated for the practical and convenient synthesis of the title compounds: The first route applies a bromination-dehydrobromination sequence to introduce the double bond into 1-alkoxycarbonyl-2-oxocycloalkylacetic and propionic esters (4a-c, 7a,b). The application of 2,6-lutidine for dehydrobromination of alpha-bromocycloalkanones diesters (5a-c, 8a, b) provides sufficient selectivity to carry out this step without affecting the sensitive ester group. Alternative pathways, involving Michael reaction of diethyl 2-acetylsuccinate or -glutarate with acrolein and subsequent intramolecular aldol condensation, are presented in the case of cyclohex-2-enone derivatives 2a, b.
A short and efficient annelation sequence for the synthesis of bicyclic intermediates in the total synthesis of strigol and its analogues
作者:I. K�das、G. �rvai、L. T�ke
DOI:10.1007/bf00807028
日期:——
A new annelation sequence was developed for the bicyclic diones 2, intermediates in the total synthesis of strigol (1) and its analogues. The first step of the sequence is the conjugate addition of nitro alcohols 4 to cyclopentenone 5, followed by an alkylative cyclization step and dehydrogenation.
Direct and indirect radical denitrations of intermediates in the synthesis of sorgolactone and its nuclear analogs+
Denitration of various important intermediates in the synthesis of sorgolactone and itsanalogs using radical chemistry on nitroketones or on the derived isocyanides is described. The nitro group is needed for the first step of the annellation process, the Michael addition of substituted nitroalkanes to cyclopentenones. Then it can be removed directly or after reduction to the amine or via the ketone
7-methyl-4-nitro-1-oxohydrindene derivatives. Functional group elaborations of these intermediates lead to a series of the title compounds, which could be readily converted to the tricyclic moieties of strigol and its analogues of biological importance.