Some caged polycyclic phosphoranes

Abstract

c) it must be emphasized that we have excluded from our considerations the initial generation of a phosphoranyi radical adduct with odd electron apical, a species resulting from equatorial introduction of attacking alkoxy radical (facial attack towards the electron lone pair). Such an intermediate might be expected to isomerize rapidly to the more stable odd-electron-equatorial radical with entering alkoxy group then either apical (as in 7 or 8) or equatorial (e.g., 9). Our results do not rule out such an attack but merely exclude any single or combination of attack routes (and subsequent isomerizations) which randomize the positions of R'O. and R20. in 4 (7, 8, 9). (12) T. B. Min. unpublished results from this laboratory.(13) Given the case that k~' be only greater than /q0, the conclusion re-mains the same. Under thls condition, k2(k+) would be less than 3.3 kp; but the increase in lifetimes of 8 and 9 would still result in equilibration and memory loss. (14) For experimentally and theoretically based estimates, see PAbstract: A series of caged polycyclic thiooxyphosphoranes and oxyphosphoranes has been prepared by allowing the dithietene 6, the dioxetane 14, and hexafluorobiacetyl to react with bicyclic phosphites. Those products which contain only sixmembered rings in the bicyclic moiety have NMR spectra which show that, over the temperature range investigated, there is a rapid intramolecular motion which renders the nuclei under investigation equivalent. On the other hand, introduction of one or more five-membered rings into the bicyclic moiety leads to an inhibition of this intramolecular process, and activation energies of 12-19 kcal/mol are found for these substances. The increase in activation energy is probably associated with an increase in strain in the five-membered ring(s) during the intramolecular isomerization.During the past several years Ramirez, Ugi, and their coworkers have prepared a number of caged polycyclic oxyphosphoranes by condensation of phosphites with hexafluoroacetone and hexafluorobiacetyl.2 Representative structures are 1-3. These substances' structures have been studied by cF3\r___rcF3 (CFd, 1 1 (CFA (CF3, (CF, k OLP,O O V o 1 2 3variable-temperature N M R measurements. The data show that the fluorines of the trifluoromethyl groups of 1 are equivalent over all the temperatures investigated. The same is true for compounds 2 and 3. Similarly, the hydrogens on the carbons bonded to oxygen of 1 are equivalent over the temperature range studied. Once again the same was found to be true for 2 and 3. No structure, trigonal bipyramid or square pyramid, can account for the N M R data, and it has been concluded by Ramirez and Ugi that there is a low-energy intramolecular exchange pathway for interconversion of trigonal-bipyramidal structures which renders the various nuclei equivalent. An alternative ionization-recombination mechanism has been considered and rejected on the basis of the lack of change of the 31P N M R chemical shifts with increasing polarity of solvent. It has been shown i...

Some acyclic pentaalkoxyphosphoranes

“…Trineopentyl Phosphite. This material was prepared according to the procedure of Relies.26 Preparation of Methyl Benzenesulfenate (9). Methyl benzenesulfenate has been prepared by Vorlander and Mittag27 in rather poor yield.…”

Stereoselective PCO/POC-Rearrangement of P–C-Cage Phosphorane in the Reaction of 4,5-Dimethyl-2-(2-oxo-1,2-diphenyl)ethoxy-1,3,2-dioxaphospholane with Hexafluoroacetone

“…Information on configurational stability of pentacoordinate phosphorus is inconsistent. On the one hand, processes of pseudorotation of phosphorus configuration are known, which lead to formation of different equilibrium forms; − on the other hand, stable pentacoordinate configurations were also reported. − It is possible that in the considered case stereoselectivity of formation of the phosphorus center is also high and is related to the configuration of the atom C 4 . Formation of two diastereoisomers in the ratio of 1.1:0.8 for compound 9 and 1:1 for 10 is then solely connected with configurations of the atoms C 7 , C 8 ( R , R / S , S ) and C 3 ( R / S ).…”

“…Their unusual skew to the same side arises because deviation of the C 7 atom from the O 1 P 2 O 3 C 4 plane is partially compensated by deviation of the C 5 atom from this plane in the same direction. Dimethyl dioxaphospholane cycle with different coordination of the phosphorus atom (III, IV, VI) usually possesses a flattened envelope conformation with a small deviation of either phosphorus or carbon atom from the ring plane. ,− …”

Describing Polytopal Rearrangements of Fluxional Molecules with Curvilinear Coordinates Derived from Normal Vibrational Modes: A Conceptual Extension of Cremer–Pople Puckering Coordinates

“…1, iron pentacarbonyl; 135 2, a spirocyclic pentaorganylsilicate; 136 3, a caged phosphorane. 137 a Units for amplitude r m and phase angles θ m /ϕ m are angstrom (Å) and degree (deg), respectively. a Units for amplitude r m and phase angles θ m /ϕ m are angstrom (Å) and degree (deg), respectively.…”

“…Three pentacoordinate compounds used to illustrate three different stereomutation mechanisms M1 through M3 , respectively, in Figure . 1 , iron pentacarbonyl; 2 , a spirocyclic pentaorganylsilicate; 3 , a caged phosphorane …”