α,α-Disubstituted Allyl Sulfones: An approach to the synthesis of vinyl-branched pheromone analogues |
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Authors: | Michal Hoskovec,Bohumí r Koutek,Josef Lazar,Ludví k Streinz,Eva Bro ov ,Blanka Kalinov ,Jan Vrko
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Affiliation: | Michal Hoskovec,Bohumír Koutek,Josef Lazar,Ludvík Streinz,Eva Brožová,Blanka Kalinová,Jan Vrkoč |
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Abstract: | The two-step alkylation of phenyl prop-2-enyl sulfone ( 1 ) with protected ω-bromoalkanols and 1-iodoalkanes (→ 3 ; see Scheme 1) followed by a Pd-catalyzed desulfonylation with LiBH4 affords a 96:4 mixture of vinylbranched, protected alcohols and corresponding ethylidene-branched isomers (see Scheme 2; 4 and 5 , respectively). By utilizing the large difference in reactivity of mono- and trisubstituted C?C bonds towards singlet oxygen, the ethylidene derivatives are easily removed from the mixture by photo-oxygenation. The vinyl-branched compounds are inert to this reaction and can be conveniently isolated in highly pure form (99.5%) and ca. 45% overall yield. |
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