Spiropentane as a tensile spring

Abstract

Health for financial support (GM 30757) and . K. O'Brien thanks the Graduate Alumni of Case Western Reserve University for the award of a Graduate Fellowship (August 1987-May 1988. Supplementary Material Available: Structural report for compound 6 giving methods for data collection, data reduction, structure solution and refinement, tables of crystal data, intensity measurements, structure solution and refinement, positional and thermal parameters, general temperature factor expressions, bond distances, bond angles, and intensity data, and a drawing of a single molecule showing 30% probability ellipsoids (22 pages); listing of observed and calculated structure factors (25 pages). Ordering information is given on any current masthead page.(16) This is the shortest total synthesis of (±)-trichodermol so far recorded, requiring 16 steps from 4-methylanlsole, which augurs well for the future use of 4 and related complexes. For comparison, Raphael's synthesis of trichodermin uses 19 steps from 4-methylanisole and was plagued by a difficult internal aldol reaction to generate the C ring. Still's synthesis of trichodermol elegantly overcomes this problem, but it involves 24 steps from 4-methylanisole (ref 2).

Koordinationschemie an Kohlenstoff: die Patchwork‐Familie bestehend aus (Ph3P)2C, (Ph3P)C(C2H4) und (C2H4)2C

“…Seine Abmessungen wurden in der Gasphase über Elektronenbeugung (ED), [80] an mindestens zwei flüssigkristallinen Phasen (LC) über NMR-Spektroskopie [80][81][82][83] und über Tieftemperatur-Einkristall-Rçntgenbeugung [84] (Fp. Seine Abmessungen wurden in der Gasphase über Elektronenbeugung (ED), [80] an mindestens zwei flüssigkristallinen Phasen (LC) über NMR-Spektroskopie [80][81][82][83] und über Tieftemperatur-Einkristall-Rçntgenbeugung [84] (Fp.…”

“…[84] Der Einfluss von Substituenten auf die relative Länge der vicinalen und distalen C-C-Bindungen kann hin-gegen beträchtlich sein, und diese Effekte kçnnen in quantenchemischen Rechnungen erfasst werden. Kristallpackungseffekte führen kaum zu Verzerrungen; deshalb wurde das Molekül auch als "dehnbare Feder" bezeichnet.…”

Non‐empirical calculations of NMR indirect carbon–carbon coupling constants. Part 7—Spiroalkanes

“…42 The experimental molecular geometry of spiropentane has been well established by electron diffraction in the gaseous state, 43,44 by NMR in the nematic phase 45,46 and also by x-ray analysis of unsubstituted spiropentane 47 and derivatives 48 in the crystalline state. HF, MP2 and DFT-B3LYP calculations of molecular geometry, isotropic magnetic shieldings (chemical shifts) and vibrational frequencies were recently performed by Dodziuk et al 49 In addition, the gas-phase protonation of spiropentane to yield C 5 H 9 C ions has been investigated by -radiolysis and FT-ICR techniques combined with ab initio calculations, 50 and also spiropentane radical cation was isolated and investigated in a CCl 3 F matrix at 4 K. 51 Going back to Table 1, spiropentane possesses the highest molecular symmetry D 2d and the largest deviation of the inter-ring bond angle at the spiro carbon (ca 137°) from the tetrahedral geometry in the series 1-7.…”

“…Ł level in comparison with those calculated at the HF, MP2 and B3LYP levels by Dodziuk et al 49 and determined experimentally by x-ray, 47 electron diffraction 43 and NMR in the nematic phase 45 are compiled in Table 2. Very good agreement of the present results with the x-ray experimental geometry was found, in line with the reported MP2 and B3LYP data.…”

Protonation sites in thiolato iron carbonylates: evidence for an arrested Fe(RS-H) oxidative addition

“…3 The I3C NMR spectrum showed that it has C2 symmetry2 and indicated the bridgehead hydrogens to be trans.…”