Lewis Acid Catalyzed Cascade Reactions of 1,6‐Diynes and 1,6‐Enynes with Vinylidenecyclopropanes

Abstract

Lewis acid catalyzed reactions of N-(4-hydroxy-4,4-diarylbut-2-ynyl)-4-methyl-N-prop-2-ynylbenzenesulfonamides or 1,1-diphenyl-4-prop-2-ynyloxybut-2-yn-1-ol (1,6-diynes) 1 and N-allyl-N-(4-hydroxy-4,4-diarylbut-2-ynyl)-4-methylbenzenesulfonamides (1,6-enynes) 2 with vinylidenecyclopropanes 3 selectively produce polycyclic compounds 4, 5 and 10 as well as isopropylidene-3,3-diarylcyclobut-1-enylmethyl derivatives 6 or 7 in good to high yields depending on the substituents on the benzene ring of 3 under mild conditions. An interesting PtCl(2)-catalyzed cyclization of 6 and a Cu(OAc)(2)H(2)O catalyzed Eglinton coupling reaction of 5 and 10 to produce the corresponding 5-isopropylidene-6-methyl-1-(toluene-4-sulfonyl)-7-vinyl-1,2,3,4,5,8-hexahydroazocine derivatives 8 and the coupling products 9 and 11 in good yields have been disclosed, respectively. Plausible mechanisms of these processes have been proposed that belong to a cascade rearrangement followed by the Friedel-Crafts reaction, an intramolecular proton transferring and a cyclization reaction.

Lewis Acid-Promoted Three-Component Reactions of Propargylic Alcohols with 2-Butynedioates and Secondary Amines

“…When morpholine ( 2g ) was used, a highly strained molecule 5 (31% yield) was isolated along with the desired product 4r (34% yield) (Scheme ). When the reaction temperature was increased to 80 °C, however, 4r could be obtained as a major product.…”

Construction of Carbocycles from Methylenecyclopropanes

“…Et 2 O‐catalyzed cascade reactions of 1,6‐diynes or 1,6‐enynes 143 with VCPs 54 also led to the multi‐aromatically fused five‐membered carbocycles 144 [Eq. (63)] …”

Recent Advances on the Lewis Acid-Catalyzed Cascade Rearrangements of Propargylic Alcohols and Their Derivatives

“…By using vinylidenecyclopropanes ( 55 ) instead of methylenecyclopropanes to perform the reaction with 1,1,3-triarylprop-2-yn-1-ols or their methyl ethers ( 56 ), the functionalized 2,4-dihydro-1H-cyclopenta­[ b ]­naphthalenes ( 57 ) and 1,2,3,8-tetrahydrocyclopenta­[ a ]­indenes ( 58 ) were successfully obtained, depending on the substrates and Lewis acids (Scheme ) . The proposed mechanism was drawn in Scheme .…”

“…In this case, the rearrangement of propargylic alcohol occurred. Using Cu(OTf) 2 as a catalyst, however, the direct alkylation of indoles with propargylic alcohols gave 3propargylic indoles (17). Further treatment with NIS, 17 could be converted to 2-iodo-1,4-dihydrocyclopenta [b]indoles (18) via the electrophilic cyclization.…”