Novel Synthesis of .alpha.-Stannyl Vinyl Ethers from Catalytic and Stoichiometric Fischer Carbene Anions

Rhodium‐Catalyzed Oxygenative Addition to Terminal Alkynes for the Synthesis of Esters, Amides, and Carboxylic Acids

“…Notably, the reaction proceeded well in wet acetonitrile to furnish the carboxylic acid 6 f as the product. From the perspective of the alkyne structure, the reaction tolerated aryl (6-9 and 16), heteroaryl (10), alkenyl (11), branched alkyl (12), and linear alkyl (13)(14)(15) substituents. Various amines also participated well in the reaction to give rise to primary (15 b), secondary (15 c), and tertiary (15 d) amides, including a Weinrebs amide (15 e).…”

“…3-picoline N-oxide 92 10 [c] 4-picoline N-oxide 95 11 2,6-lutidine N-oxide 13 12 8-methylquinoline N-oxide 54 [a] . nucleophile, the reaction occurred exclusively at the amino group in preference to the alcohol, thus providing the N-acyl product 15 f. These amide-forming reactions benefited from the use of ammonium salts rather than free amines as nucleophiles, as higher yields were consistently obtained from the reactions of amine salts compared to those of the free amines.…”

Metal Vinylidenes as Catalytic Species in Organic Reactions

“…For example, homopropargyl alcohol 64 could be converted to α-(tributylstannyl)dihydrofuran 97 in reasonable yield with a catalytic amount of a molybdenum pentacarbonyl complex and tributyltin triflate (equation 1, Scheme 28). [46] The bis-homopropargyl alcohol 98, on the other hand, could only be converted to a Fischer carbene by treatment with a tungsten pentacarbonyl complex. Upon treatment with the tin reagent, α-(tributylstannyl)dihydrofuran 100 was then obtained in quantitative yield (equation 2).…”

Alkynolendo-Cycloisomerizations and Conceptually Related Transformations

“…Along these lines we discovered a new and very mild method for preparing alpha-stannyl vinyl ethers 5 based on molybdenum-catalyzed cyclization of alkynyl alcohols 1 in the presence of tributyltin triflate. [10] Although molybdenum-catalyzed cyclizations are largely limited to five-membered ring formation, we have discovered that tetrahydrofuran-tungsten pentacarbonyl is an effective reagent for cyclizations of 1-alkyn-5-ols 6 leading to production of six-membered rings (Scheme 6). [11] The stoichiometric 1-Alkyn-5-ol substrates 14 bearing oxygen substituents at the propargylic position (C 3 ) rapidly react with the tungsten pentacarbonyl reagent, but these substrates tend to give mixtures of regioisomeric metal-free products, and favors the five-membered exocyclic enol ether 15 when the cyclization reaction is conducted at room temperature.…”