d⁵‐Reactions of Doubly Deprotonated γ,δ‐Unsaturated Carbonyl Derivatives with Electrophiles. A Novel Approach to the Synthesis of Tetrahydrofuran and Tetrahydropyran Derivatives

Abstract

SummaryThe dienone-dianion derivatives 1 react with all types of electrophiles tested (alkyl halide, silyl chloride, ester, ketone, aldehyde, epoxide) to give 8, y-unsaturated carbonyl compounds of type A (see Formulae 2-6, 13, 14 and Tables 1-5). The aand p-hydroxyalkylation products obtained from la-ld can be converted to tetrahydrofuran and tetrahydropyran derivatives 7 and 16, respectively (Tables I and 2), those from the sulfur analogues le and If to ketene thioacetals 9 and to dienone derivatives 10 and 12. The t-butyl and a-hydroxy-ketones are cleaved to give nitriles, amides, carboxylic acids and esters (Formulae 16-25). The reagents 1 allow to synthesize products with distant functional groups in one step (cf. 1,g-diketones 14 and Formulae 26-30); they correspond to the d5-synthons 31-33; in Table 6, they are compared with other ds-reagents.

Diastereoselective oxygen to carbon rearrangements of anomerically linked enol ethers and the total synthesis of (+)-(S,S )-(cis-6-methyltetrahydropyran-2-yl)acetic acid, a component of civet

“…The combined organic extracts were dried (MgSO 4 ), filtered, and the solvent evaporated in vacuo to leave a yellow oil which was purified by flash column chromatography, eluting with 20% ethyl acetate-petroleum ether (bp 40-60 ЊC) to give 22 (145 mg, 68%) as a colourless oil. [α] D 31 ϩ20.5 (c 1.23, CHCl 3 ) [lit., 23…”

A Short Synthesis of (R,R)‐(‐)‐Pyrenophorin from (S)‐Propylene Oxide and a 3‐Pentenoic Acid d5‐Reagent

“…These d5-reagents combine with electrophiles exclusively at the terminal carbon to give b,y-unsaturated ketones 4. The R groups in 3/4 are chosen, so that eventually the corresponding conjugated or non-conjugated unsaturated carboxylic acids 5 can be prepared [4a + 5 by Beckmann rearrangement, 4 b -+ 5 by periodate cleavage] ' s 2 , [30][31][32][33][34][35]. Since epoxides (az-reactivity) have turned out to be especially good electrophiles towards these d'-reagents 35), the synthetic analysis outlined in Scheme 2 was envisaged for pyrenophorin (1).…”