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.

Although numerous reports exist on strained C-C bond cleavage reactions in aryl substitutions, the cleavage methodology for unstrained C-C bonds in alkylation reactions has not yet been established. We found that unstrained allylic C-C bonds can be cleaved using α-radicals to form C(sp )-C(sp ) bonds in the presence of a copper catalyst. In this reaction, the property of leaving and loading radicals is very important for radical fragmentations. In this paper, we investigated the effects of these properties in cleavage reactions for unstrained C-C bonds.

No abstract

Condensation products of oleic acid and paraformaldehyde in acetic acid solution were saponified and then fractionated by recrystallization, and the following two substances were obtained [1 part

A Copper-Catalyzed Formal [3 + 2]-Cycloaddition for the Synthesis of All Different Aryl-Substituted Furans and Thiophenes. -Tetraarylfurans are highly efficiently obtained starting with a formal [3+2]-cycloaddition of various widely available styrenes and bromo keto esters affording diaryl-substituted dihydrofurans followed by oxidation to give diarylfurans and sequential arylations. Tetraarylthiophenes can be obtained in similar manner after the conversion of the diaryl-substituted dihydrofurans into dihydrothiophenes with Lawessons reagent. -(ISHIKAWA, S.; NODA, Y.; WADA, M.; NISHIKATA*, T.; J. Org. Chem. 80 (2015) 15, 7555-7563, http://dx.doi.org/10.1021/acs.joc.5b01139 ; Grad. Sch. Sci. Eng., Yamaguchi Univ., Ube, Yamaguchi 755, Japan; Eng.) -Toeppel 51-109