Octalones Nazarov cyclization

A usefid feature of the Nazarov cyclization is the construction of fused bicyclic systems by annulation of a flve-membered ring. This requires one of the vinyl groups to be embedded in a ring. These precursors can be formed easily by vinyl alkyne addition to cyclic ketones followed by dehydration and hydrolysis. This procedure woiks well for symmetrical ketones but it gives regioisomers from unsymmetrical ketones such as 1- or 2-octalone."- A superior method, reported by Paquette, 76 involves the acylation of cycloalkenylsilanes to provide divinyl ketones (equation 6). The advantages of this protocol are discussed in Section 6.3.7.4.3. 

Thus, the condensation of vinylacetyl bromide with cyclohexene in presence of aluminium chloride led to ketone S (68 % yield) and octalone 9 (17 %). The divinyl ketone S may be formed during the work-up, since, in the reaction conditions, S itself, must undergo the Nazarov cyclization. 

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See also in sourсe #XX -- [ , ]

See also in sourсe #XX -- [ ]

See also in sourсe #XX -- [ , ]

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