Preparation of 2,3-Dihydrofurans via a Double Allylic Substitution Reaction of Allylic Nitro Compounds

Gold-catalyzed formal (3 + 2) and (4 + 2) cycloaddition reactions using propiolates: assembly of 2,3-dihydrofurans and 3,4-dihydropyrans via a multistep cascade process

A gold-catalyzed formal dipolar cycloaddition reaction was developed using polarized alkynes as dipolarophiles and butenediol or pentenediol derivatives as formal dipoles. Silyl groups were used to solve the selectivity issue of unsymmetrical diols.

Highly regio- and stereoselective phosphinylphosphination of terminal alkynes with tetraphenyldiphosphine monoxide under radical conditions

The homolytic cleavage of the P^V(O)–P^III bond in tetraphenyldiphosphine monoxide simultaneously provides both pentavalent and trivalent phosphorus-centered radicals with different reactivities. The method using V-40 as an initiator is successfully investigated for the regio- and stereoselective phosphinylphosphination of terminal alkynes giving the corresponding trans-isomers of 1-diphenylphosphinyl-2-diphenylthiophosphinyl-1-alkenes in good yields. The protocol can be applied to a wide variety of terminal alkynes including both alkyl- and arylalkynes.

Annulation of β-naphthols and 4-hydroxycoumarins with vinylsulfonium salts: synthesis of dihydrofuran derivatives

A new synthetic approach to dihydrofuran derivatives via the annulation reaction of β-naphthols and 4-hydroxycoumarins with vinylsulfonium salts has been developed. A variety of dihydrofuran derivatives were prepared in moderate to good yields under mild conditions. The products could be readily transformed to the corresponding furans via the dehydrogenation with DDQ.

Synthetic Approach to the Preparation of (2-Acetoxy)allyl Nitro Compounds

A synthetic approach to a new class of allyl nitro derivatives is reported. (2-Acetoxy)allyl nitro compounds have been prepared for the first time in a four-step procedure by a preliminary reaction of nitroalkanes with 2-(phenylselenyl)acetaldehyde. After the acetylation of the obtained nitro alcohols, the unsaturation is installed by an oxidation reaction involving the phenylselenyl group followed by a thermal elimination. The oxidation process is accomplished under flow conditions ensuring a notable lowering of overoxidation by products observed in batch.

Palladium triggered diene formation from nitro allylic compounds: a versatile entry into naphthalene derivatives

Dienes from Tsuji–Trost elimination of nitrite: a powerful access to functionalized naphthalenes.

Copper-catalyzed tandem trifluoromethylation–cyclization of olefinic carbonyls: synthesis of trifluoromethylated 2,3-dihydrofurans and 3,4-dihydropyrans

A copper-catalyzed trifluoromethylation–cyclization of olefinic carbonyls was developed. With this method, a variety of 2,3-dihydrofuran and 3,4-dihydropyran derivatives containing a CF₃ group were selectively obtained in moderate to good yields.

Sc(OTf)3-catalyzed cyclization of α-allylated 1,3-dicarbonyls: an efficient access to 2,2-disubstituted 2,3-dihydrofuran derivatives

A Sc(OTf)₃-catalyzed cyclization of α-allylated 1,3-dicarbonyls is reported. By the reaction, a variety of 2,2-disubstituted 2,3-dihydrofurans were obtained in good yields.

A Copper-Catalyzed Formal [3 + 2]-Cycloaddition for the Synthesis of All Different Aryl-Substituted Furans and Thiophenes

A highly efficient formal [3 + 2]-cycloaddition was established using a copper catalyst. The resulting dihydrofurans were subjected to oxidation followed by arylations to produce tetraarylfurans. In addition, the dihydrofuran can be converted to diaryldihydrothiophene by using Lawesson's reagent. This protocol will facilitate the synthesis of all different aryl-substituted furans and thiophenes.

Copper-mediated tandem reaction of β-ketoesters/ketones with tertiary amines for the synthesis of 2,3-dihydrofurans

A novel synthetic method of 2,3-dihydrofuran using β-ketoester and TMEDA as starting materials has been developed.