Structures of Two Diastereomeric Aldol Products from a New Silicon-Directed Condensation

Abstract

Hexahydro-3,3,6-trimethyl-5-phenyl- 1 <i>H,7H</i>-pyrrolo[2,1-<i>e</i>][1,3,6,2]dioxazasilonin-7-one, C₁₇H₂₅NO₃Si, M_r=319.48. (2<i>S</i>,3<i>R</i>)-<i>anti</i>-Diastereomer (I), orthorhombic, <i>P</i>2₁2₁2₁, <i>a</i>= 8-716(4), <i>b</i>=11-677(3), <i>c</i>=17.161(6)A, <i>V</i>=1746(1)A³, <i>Z</i>=4, <i>D</i>_x=1.22 g cm^-3, wavelength(Mo Kce) = 0.71073 A, <i>u</i>=1.50 cm^-1 F(000)=688, room temperature, final <i>R</i>=0.040 for 1683 reflections with F_o² greater than 0. (2S,3S)-<i>syn</i>- Diastereomer (II), monoclinic, P2₁, <i>a</i>=6.633(2), <i>b</i>=14.645(3), <i>c</i>=9.630(2) A, Beta=109.96(2)^o, <i>V</i>=879.3(4) A³, <i>Z</i>=2, D_x=1.21 g cm^-3, wavelength(Mo K<i>a</i>)=0.71073 A,<i>u</i> = 1-49 cm^-1, <i>F</i>(000)=344, room temperature, final R = 0.042 for 2537 reflections with F²_o greater than 0. The compounds have a nine-membered hetero-cyclic ring containing the Si atom, the N atom of the pyrrolidine ring, two O atoms bonded to silicon and a carbonyl C atom. Bond distances in the molecules are normal and equivalent bonds are equal within three times their e.s.d.'s. Isomer (I) shows a disorder in the pyrrolidine ring that is absent in isomer (II).