Imino-Diels-Alder Adducts. Part XIII. Polymorphism in Pyrano [3,2-c] Quinolines
作者:Krishnan Ravikumar、Balasubramanian Sridhar、Masna Mahesh、Vaddu Venkata Narayana Reddy
DOI:10.1007/s10870-007-9260-3
日期:2008.1
Crystallization by slow evaporation of methanol solution of 5-(4-nitrophenyl)-3,4,4a5,6,10b-hexahydro-2H-pyrano[3,2-c] quinoline, yields two polymorphs. Rectangle plate-like crystals have a triclinic (P $$ \ifmmode\expandafter\bar\else\expandafter\=\fi1} $$ ) structure, with one molecule in the asymmetric unit, a = 8.2299(5) Å, b = 9.7774(6) Å, c = 11.0047(7) Å, α = 65.718(1)°, β = 75.699(1)° and γ = 71.617(1)°, while, long needle-like crystals exhibit a monoclinic (C2/c) crystal structure in which two independent molecules comprise the asymmetric unit, a = 32.285(3) Å, b = 9.4045(7) Å, c = 22.804(2) Å and β = 114.965(1)°. The crystal structures reveal the molecule in both the polymorphs as an endo-Imino-Diels-Alder cycloadduct isomer. The stereochemistry of the pyran ring in both the polymorphs is exo to the quinoline ring formed in the cycloaddition step. The molecules are linked by N–H···O hydrogen bonds into centrosymmetric dimers forming R2 2(18) rings in the triclinic form, while they are arranged to form a helical chain in the monoclinic form. Crystallization by slow evaporation of methanol solution of 5-(4-nitrophenyl)-3,4,4a5,6,10b-hexahydro-2H-pyrano[3,2-c] quinoline, yields two polymorphs. The crystal structures reveal the molecule in both the polymorphs as an endo-Imino-Diels-Alder cycloadduct isomer. The stereochemistry of the pyran ring in both the polymorphs is exo to the quinoline ring formed in the cycloaddition step. The molecules are linked by N–H···O hydrogen bonds into centrosymmetric dimers forming R2 2(18) rings in the triclinic form, while they are arranged to form a helical chain in the monoclinic form.
通过缓慢蒸发 5-(4-硝基苯基)-3,4,4a5,6,10b-六氢-2H-吡喃并[3,2-c]喹啉的甲醇溶液结晶,可得到两种多晶体。矩形板状晶体具有三菱(P $ \ifmmode\expandafter\barse\else\expandafter\=\fi1} $$ )结构,不对称单元中有一个分子,a = 8。2299(5) Å, b = 9.7774(6) Å, c = 11.0047(7) Å, α = 65.718(1)°, β = 75.699(1)°和γ = 71.617(1)°,而长针状晶体呈现单斜(C2/c)晶体结构,其中两个独立分子构成不对称单元,a = 32.285(3) Å,b = 9.4045(7) Å,c = 22.804(2) Å,β = 114.965(1)°。晶体结构显示,该分子在两种多晶型中都是内-内-Diels-Alder 环加载异构体。这两种多晶型中吡喃环的立体化学结构与环化步骤中形成的喹啉环的立体化学结构相同。这些分子通过 N-H-O 氢键连接成中心对称的二聚体,在三linic 形中形成 R2 2(18) 环,而在单linic 形中则排列成螺旋链。通过缓慢蒸发 5-(4-硝基苯基)-3,4,4a5,6,10b-六氢-2H-吡喃并[3,2-c] 喹啉的甲醇溶液进行结晶,可以得到两种多晶体。晶体结构显示,这两种多晶型中的分子都是内离子-Diels-Alder 环加载异构体。这两种多晶型中吡喃环的立体化学结构与环化步骤中形成的喹啉环的立体化学结构相同。这些分子通过 N-H-O 氢键连接成中心对称的二聚体,在三linic 型中形成 R2 2(18) 环,而在单linic 型中则排列成螺旋链。