Mercury in organic chemistry. 24. Mercuration and subsequent carbonylation of 4-hydroxy-2-alkyn-1-ones: a novel route to furans

Abstract

Mercuric chloride readily adds to the carbon-carbon triple bond of certain 4-hydroxy-2-alkyn-l-ones (3a, 3b, and 3e) to give vinylmercurials which appear to be the first syn addition compounds of mercuric chloride. These vinylmercurials readily dehydrate to 3-furylmercurials. Palladium-promoted carbonylation of these compounds affords 3-furyl carbonyl compounds.Mercury(II) salts are known to readily add to a variety of acetylenes to afford vinylmercurials (eq 1). Thus, Cl, OAc, SON mercuric halides are reported to add to acetylene (anti),2"7 propyne (anti),8 cyclooctyne,® vinylacetylene (anti?),8•10 11"12

Arylnaphthalene Lignans through Pd‐Catalyzed [2+2+2] Cocyclization of Arynes and Diynes: Total Synthesis of Taiwanins C and E

“…With the aim of synthesizing the taiwanins, substrates 3 a-3 d were synthesized as shown in Scheme 4. Diynes 3 a and 3 b were prepared by DCC-mediated esterification of carboxylic acid 5 [11] with the corresponding propargylic alcohols 6 a and 6 b, [12] respectively. Diyne 3 c was synthesized by similar esterification of 5 with 6 c [13] followed by cleavage of the TBS protecting group of 7 and oxidation of the corresponding alcohol to the aldehyde.…”

Synthesis of Biaryls via Palladium‐Catalyzed [2+2+2] Cocyclization of Arynes and Diynes: Application to the Synthesis of Arylnaphthalene Lignans

“…Following the similar procedure for 3a, the crude product, which was prepared from the carboxylic acid 17 (200 mg, 1.1 mmol), the propargylic alcohol 18b [19] (181 mg, 1.6 mmol), DMAP (39 mg, 0.32 mmol), and DCC (326 mg, 1.6 mmol) in CH 2 Cl 2 (5 mL) at room temperature for 20 min, was purified by column chromatography on silica gel (hexane/AcOEt = 3/1) to give 3b as an off-white solid (19) Following the similar procedure for 3a, the crude product, which was prepared from 17 (82 mg, 0.42 mmol), the propargylic alcohol 18c [20] …”

Synthesis of Heterocycles and Carbocycles by Electrophilic Cyclization of Alkynes

“…Propargylic alcohols react with HgCl 2 to generate vinylic mercurials that are readily cyclized to furylmercurials [5] (Equation 2.4) or carbonylated to butenolides (Equation 2.5) [6].…”

“…Metal salts of Pt(ii), Pd(ii), Au(iii), and Cu(i), for example, will cyclize acetylenic vinylic ethers in the presence of methanol to produce five-and six-membered ring carbocyclic acetals (Equation 2.139) [190]. Acetylenic enol silanes have been cyclized by treatment with catalytic amounts of PtCl 2 [188] or W(CO) 5 [192]. Acetylene-containing enol silanes also smoothly cyclize in the presence of HgCl 2 to afford vinylmercurials, which have subsequently been cleaved by protic acids or halogenating agents (NBS, NIS) or carbonylated to esters (CO, MeOH, PdCl 2 , CuCl 2 , LiCl) to afford a wide variety of cyclic, bicyclic, and spirocyclic unsaturated ketones and several natural products (Equation 2.142) [193].…”