182008-96-4Relevant academic research and scientific papers
Synthesis of spiroacetal enol ethers via intramolecular conjugate addition of hemiacetal alkoxides to alkynoates
Toshima, Hiroaki,Furumoto, Yoshinori,Inamura, Shintaro,Ichihara, Akitami
, p. 5707 - 5710 (1996)
(E)- and (Z)-2-Methoxycarbonylmethylene-1,6-dioxaspiro[4.5]decane (12E, 12Z) have been constructed from the acyclic keto alcohol 11a possessing an alkynoate part under the basic conditions. By the thermodynamic control, 12E could be obtained in high selectivity. Under several basic and acidic conditions, 12Z could be isomerized to 12E.
Asymmetric Synthesis of Spiroketals with Aminothiourea Catalysts
Yoneda, Naoki,Fukata, Yukihiro,Asano, Keisuke,Matsubara, Seijiro
supporting information, p. 15497 - 15500 (2016/01/26)
Chiral spiroketal skeletons are found as core structures in a range of bioactive compounds. These natural compounds and their analogues have attracted much attention in the field of drug discovery. However, methods for their enantioselective construction are limited, and easily available optically active spiroketals are rare. We demonstrate a novel catalytic asymmetric synthesis of spiroketal compounds that proceeds through an intramolecular hemiacetalization/oxy-Michael addition cascade mediated by a bifunctional aminothiourea catalyst. This results in spiroketal structures through the relay formation of contiguous oxacycles, in which multipoint recognition by the catalyst through hydrogen bonding imparts high enantioselectivity. This method offers facile access to spiroketal frameworks bearing an alkyl group at the 2-position, which are prevalent in insect pheromones. Optically active (2S,5S)-chalcogran, a pheromone of the six-spined spruce bark beetle, and an azide derivative could be readily synthesized from the bicyclic reaction product. Around and around: A catalytic asymmetric synthesis of spiroketals through an intramolecular hemiacetalization/oxy-Michael addition cascade with a bifunctional aminothiourea catalyst was developed. This method offers facile access to spiroketal frameworks bearing an alkyl group at the 2-position. Optically active (2S,5S)-chalcogran, a pheromone from the six-spined spruce bark beetle, and a derivative were readily synthesized from the bicyclic reaction product.
Highly stereoselective syntheses of spiroacetal enol ethers, (E)- and (Z)-methoxycarbonylmethylene-1,6-dioxaspiro[4,5]decanes
Toshima, Hiroaki,Aramaki, Hisateru,Furumoto, Yoshinori,Inamura, Shintaro,Ichihara, Akitami
, p. 5531 - 5544 (2007/10/03)
(E)- and (Z)-2-methoxycarbonylmethylene-1,6-dioxaspiro[4,5]decanes have been synthesized from an acyclic keto alcohol possessing an alkynoate part via intramolecular conjugate addition. Under thermodynamically controlled conditions using t-BuOK in THF, the (E)-isomer could be obtained in 52:1 ratio. When a catalytic amount of Pd(OAc)2 was used in benzene, the (Z)- isomer could be obtained in 95:1 ratio.
