Direct furan formation by treatment of alkynyl ketones with strong potassium bases
作者:David I. MaGee、James D. Leach、Santosa Setiadji
DOI:10.1016/s0040-4020(99)00063-0
日期:1999.3
The reaction of keto-alkynes with strong potassium bases such as KOtBu, KHMDS or KH yields substituted furans in moderate to good yields without any special activation of the alkyne required. The method offers both a flexibility and rapid method for the synthesis of di- tri- or tetra-substituted furans, although some yields are only modest at best.
A new furan annelation by the palladium-catalyzed reaction of 2-alkynyl carbonates with β-keto esters is described. The reaction proceeds under mild neutral conditions and hence unstable 3-alkylidene-2,3-dihydrofurans can be prepared in this way. Similarly, reaction of 2-(1-alkynyl)oxiranes with β-keto esters gives alkylidene furans.
Preparation of unstable 3-alkylidene furans by the palladium-catalyzed reaction of α-alkynyl epoxides with β-keto esters
作者:Ichiro Minami、Masami Yuhara、Jiro Tsuji
DOI:10.1016/s0040-4039(00)95798-8
日期:——
Palladium-catalyzed reaction of α-alkynyl epoxides with β-keto esters gives unstable 3-alkylidene-2,3-dihydrofuran-4-carboxylates. It can be carried out under mild neutral conditions, and offers a good preparative method for 3-alkylidene furans.
La reactionde carbonates de propargyl(I) avecdes carbonucleophiles doux en presence de palladium donne des propenes disubstitues en 2,3 dans des conditions neutres. Les β-cetoesters et les β-dicetones portant deux hydrogenes actifs reagissent avec I dans le rapport 1/1. Il se produit a la fois une C- et une O-alkylation avec ces composes pour donner des methylene-4 dihydro-4,5 furannes et methyl-4
La 反应 de carbonates de propargyl(I) avec des carbonucleophiles doux en存在 de palladium donne des propenes dissubstitues en 2,3 dans des conditions neutres。Les β-cetoesters et les β-dicetones portant deux hydroes actifs reagissent avec I dans le rapport 1/1。Il se produit a la fois une C- et une O-烷基化反应组成浇注 donner des methylene-4 dihydro-4,5 furranes etmethyl-4 furanes
Iodoenolcyclisation of 2-(1,3-disubstituted-1-allyl)-1,3-dicarbonyl compounds: diastereoselective synthesis of tetrasubstituted dihydrofurans
The I2-induced cyclisation of 2-alkenyl-1,3-dicarbonyl compounds with the mono- and di-substituted double bond occurred with good diastereoselectivity. A study of stereochemical aspects for different substituents on the allyl side chain was carried out. When the substituents were alkyl groups, the trans isomers formed preferentially, in the case of aromatic substituents the reaction lead instead to
I 2诱导的具有单和双取代双键的2-烯基-1,3-二羰基化合物的环化反应具有良好的非对映选择性。对烯丙基侧链上不同取代基的立体化学方面进行了研究。当取代基为烷基时,反式异构体优先形成,在芳族取代基的情况下,反应代替顺式异构体。