Room-Temperature Metallation of 2-Substituted 1,3-Dithiane Derivatives and Subsequent Coupling with 2,3-Disubstituted Oxiranes

Abstract

2-Substituted 1,3-dithiane derivatives, (S)-1-(t-butyldiphenylsiloxy)-2-(1,3-dithian-2-yl)propane (9), (S)-1-(t-butyldimethylsiloxy)-2-(1,3-dithian-2-yl)propane, 1-(t-butyldiphenylsiloxy)-2-(1,3-dithian-2-yl)-2-methylpropane, and 1,2-bis(t-butyldiphenylsiloxy)-3-(1,3-dithian-2-yl)propane, were subjected to lithiation in THF with n-BuLi at room temperature (r.t.); the resulting anions reacted with 2,3-disubstituted oxirane, trans-2-methyl-3-(triphenylmethoxymethyl)oxirane (22), at r.t., giving the coupling products in satisfactory yield. On the other hand, the lithium salt formed in ether from (S)-2-(1,3-dithian-2-yl)-1-(4-methoxybenzyloxy)propane with n-BuLi at r.t. reacted with 22 at r.t. in the presence of hexamethylphosphoric triamide to afford the coupling product in moderate yield. In addition, a mixed organometallic reagent, n-BuLi / Bu2Mg, was found to be an effective metallation reagent for 9 and the resulting anion reacted with 22 to afford the coupling product in good yield.

Total Synthesis and Confirmation of the Revised Structures of Azaspiracid‐2 and Azaspiracid‐3

“…[3b] The organometallic species derived from dithiane 6 and nBuLi/nBu 2 Mg [16] was treated with 4 at À90 8C to afford ketone 34 in 65 % yield. Treatment of 34 with DIBAL-H at À90 8C led to reduction of the carbonyl group at C20 and concomitantly cleaved the pivaloate ester group to give a dihydroxy compound from which the cyclic silyl ether was dismantled (TBAF) to afford tetraol 35 (47 % overall yield for the two steps).…”

Reiterative epoxide-based strategies for the synthesis of stereo-n-ads and application to polypropionate synthesis. A personal account

“…Epoxide 13 was obtained from chiral epoxide 22 using our reiterative approach previously discussed [26,36]. The resulting epoxide was cleaved with 1,3-dithiane using a modified Nakata procedure,[44] yielding 66% of diol 23 that contained the desired stereotetrad (Scheme 7). The absolute stereochemistry of the diol was confirmed by X-ray crystallography as being 2R,3S,4R,5R [45].…”

Synthesis and Biological Activities of Simplified Analogs of the NaturalPKCLigands, Bryostatin‐1 and Aplysiatoxin

“…Asymmetric Keck's allylation of 11 provided 12 , which was followed by Smith's iodocarbonate cyclization reaction, methanolysis, and protection, to yield the epoxide 13 . Coupling of the epoxide moiety in 13 with the dithiane unit 14 following the protocol of Ide and Nakata, and subsequent conversions provided the aldehyde 15 . Keck's allylation of 15 produced then the homoallylic alcohol 16 , which was hydrolyzed to form the desired spiroketal 17 in 49% yield.…”