Cyclization of o-(3-Hydroxy-3-methylbutynyl)phenols with Boron Tribromide to 4-Bromo-2,2-dimethylchromenes and Their Electroreduction to 2,2-Dimethylchromenes
摘要:
Cyclization of o-(3-hydroxy-3-methylbutynyl)phenols (2) with boron tribromide gave easily 4-bromo-2,2-dimethylchromenes (3). Electrolytic reduction of 3 at a Hg-pool electrode afforded the corresponding 2,2-dimethylchromenes (6) in high yields.
l-Proline derived nitrogenous steroidal systems: an asymmetric approach to 14-azasteroids
作者:Ritesh Singh、Gautam Panda
DOI:10.1039/c3ra42272k
日期:——
intramolecular SN2′ cyclization reaction for the construction of critical C-ring in the nitrogen impregnated steroidal architectures bearing unsaturation at Δ9(11) position. In the endeavour to synthesize some new congeners, the remote electronic impact of the electron donating groups in A ring and heteroatoms like oxygen in Bring, on the propensity of C-ring cyclization was also observed.
已经描述了在温和的反应条件下使用L-脯氨酸来访问14-氮杂类固醇的有效手性池方法。关键步骤涉及分子内的S N 2'环化反应,以在含氮的甾族结构中在Δ9 (11)位置携带不饱和键,以构建关键的C环。为了合成一些新的同类物,还观察到了A环上给电子基团和B环上的氧等杂原子对C环环化倾向的远程电子影响。
Synthesis and reactivity of some 3,4-dibromo-2H-[1]benzopyrans: The generation and reactions of 3,4-didehydro-2H-[1]benzopyran
作者:Christopher D. Gabbutt、John D. Hepworth、B.Mark Heron、Md.Moshfiqur Rahman、Simon J. Coles、Michael B. Hursthouse
DOI:10.1016/s0040-4020(99)00571-2
日期:1999.8
Reaction of 3,4-dibromo-2,2,6,8-tetramethyl-2H-[1]benzopyran with either organolithium reagents or magnesium generates the novel strained alkyne, 3,4-didehydro-2H-[1]benzopyran. Cycloaddition with furans gives access to the dibenzo[b,d]pyran system.
Application of Nazarov type electrocyclization to access [6,5,6] and [6,5,5] core embedded new polycycles: an easy entry to tetrahydrofluorene scaffolds related to Taiwaniaquinoids and C-nor-D homosteroids
作者:Ritesh Singh、Gautam Panda
DOI:10.1039/c0ob00892c
日期:——
An easy, efficient and concise approach to tetrahydrofluorene [6,5,6]ABC tricyclic core embedded new polycycles has been achieved under relatively mild and catalytic Nazarov type electrocyclization conditions, using 2 mol% of Sc(OTf)3 in anhydrous DCM (dichloromethane) at room temperature, with high yields. The generality of the reaction has been illustrated by synthesizing diverse polycycles embedded with rare heterotricyclic [6,5,5]ABC skeletons.
Synthesis and reactivity of some 4-bromo- 2H-chromenes and 2H-thiochromenes
作者:Christopher D Gabbutt、David J Hartley、John D Hepworth、B.Mark Heron、Magan Kanjia、M.Moshfiqur Rahman
DOI:10.1016/s0040-4020(01)86967-2
日期:1994.2
synthesis of 4-bromo- 2H-chromenes and 2H-thiochromenes and of 1-bromo-3,4-dihydronaphthalene from the corresponding ketones and PBr3 is described. In some instances, significant quantities of the phosphonic acids (3) are isolated. Conversion of the bromo compounds to the lithio derivatives provides access to a wide range of novel 4-substituted 2H-chromenes and 2H-thiochromenes.
Reactions of some 2H-Chromenes and 2H-Thiochromenes with triazolinediones
作者:Christopher D. Gabbutt、John D. Hepworth、B. Mark Heron
DOI:10.1016/0040-4020(95)00874-8
日期:1995.11
Simple 2H-chromenes and 2H-thiochromenes form the [2+2]-adducts, tetrahydro[1]benzo(thio)pyrano[3,4-c] [1,2]diazeto[1,2-a][1,2,4]triazoles, with triazolinediones, whereas their 3- and 4-bromo and the corresponding cycloalkylamino derivatives undergo an overall etectrophilic substitution sequence.