Diketones from ozonolysis of fused 3-phospholene oxides: Cyclizations to 3-phosphorinone and to 1,4-dihydro-1,4-azaphosphinine derivatives

1-R-3-Methyl-2,4,5,6,7,7a-hexahydro-1(H)-phosphindole 1-oxide and 1-R-3-methyl-6-methoxy-2,8,9,9a-tetrahydro-1(H)-benzo[e]phosphindole 1-oxide (R = Me or Ph) were prepared and ozonized at −78°C to give diketones in good yield. The intramolecular aldol condensation was performed on certain of these ketones to give multicyclic 3-phosphorinone derivatives. In some cases, double-bond rearrangement into the ring-fusion position was encountered. The 1-phenyl derivative in the benzophosphindole series could not be cyclized due to ready displacement of the P fragment from the tetralone system. The diketones reacted with ammonium acetate to give multicyclic derivatives of the 1,4-dihydro-1,4-azaphosphinine ring system. 1,2,3,4,5,6,7,8-Octahydro-3-oxo-1-phenylphosphinoline 1-oxide was used to demonstrate the value of the bicyclic 3-phosphorinones as precursors of 1-phosphadecalone derivatives. The carbonyl group was protected as the ethylene ketal and the double bond (as well as the benzene ring) was hydrogenated with ease. Hydrolysis gave the 1-phospha-3-decalone derivative. Reduction of the same 3-phosphorinone with NaBH₄ gave a mixture of diastereomeric alcohols.     

Diels-Alder adducts of 4-chloro-1,6-dihydrophosphinine derivatives: A new precursor of 2-phosphapropene

The 4-chloro-1,6-dihydrophosphinine derivatives, prepared as a mixture of 3- and 5-methyl isomers from the thermolysis of dichlorocarbene adducts with 1-R-3-methylphospholene oxide (R  Me, MeO, EtO, n-PrO, i-PrO), participate in Diels-Alder reactions with dimethyl acetylenedicarboxylate and N-phenylmaleimide. The former reactant is of special value since the 2-phosphabicyclo[2.2.2]octa-5,7-diene framework is thermally labile and undergoes retrocycloaddition by a different path, eliminating the C P bridging unit as a low-coordinate species. Thus, in the case of R  Me, the initial phosphine oxides (a mixture of isomers) have been reduced to the phosphines and these undergo straightforward fragmentations on heating at 50°C to produce 2-phosphapropene. The reactions of this transient species with water and alcohols have been investigated. Unlike the case of stabilized phosphaalkenes, hydration occurs smoothly without catalysis to produce Me₂P(O)H; addition of alcohols gives phosphinites, Me₂POR. The structure of the Diels-Alder adducts was confirmed by ³¹P, ¹H, and ¹³C NMR spectroscopy. Each of the isomeric 1,6-dihydrophosphinine oxides gives two diastereomeric adducts; partial separation of some of the resulting four-component mixtures was achieved with silica gel chromatography.     

Multiple periodic solutions for a nonlinear suspension bridge equation

We investigate nonlinear oscillations in a fourth-order partialdifferential equation which models a suspension bridge. Previouswork establishes multiple periodic solutions when a parameterexceeds a certain eigenvalue. In this paper, we use Leray-Schauderdegree theory to prove that if the parameter is increased further,beyond a second eigenvalue, then additional solutions are created.     

The reaction to the J = 2, 4.46 MeV level in Ne

We have used measurements of the reaction to deduce spectroscopic factors for the three j_n values which contribute to the transition to the 4.46 MeV level in ²²Ne. The results agree with the shell-model calculation of Preedom and Wildenthal.     

Syn to anti isomerization and degradation of phosphines of the 7-phosphanorbornene system by action of methanol

$\text{Syn}$-Substituted phosphines of the 7-phosphanorbornene system form unstable phosphorane adducts with methanol that either fragment by retro-McCormack cycloaddition or undergo polytopal rearrangement and loss of methanol to give the first examples of $\text{anti}$ phosphines.     

The 21N(→d,p)22Ne reaction to the Jπ = 2+, 4.46 MeV level in 22Ne

We have used measurements of the ${}^{21}\text{Ne(}\text{→d}\text{,p)}{}^{22}\text{Ne}$ reaction to deduce spectroscopic factors for the three j_n values which contribute to the transition to the 4.46 MeV level in ²²Ne. The results agree with the shell-model calculation of Preedom and Wildenthal.     

A New Technique for the Generation of Alkyl Metathiophosphates

Abstract

We have recently described a technique for the generation of alkyl metaphosphates, ROPO₂, by thermolysis of phosphoramidic acids of structure ROP(O)(OH)NHR (1) [1]. We have now successfully shown that alkyl metathiophosphates, ROP(S)(O), which have received but little previous consideration [2], can be generated by the same approach. Compounds 2 (Ad = 1-adamantyl) and 3 were synthesized for this study. Both were easily fragmented on heating in an inert solvent. When an alcohol trapping agent was present each gave EtO-P(S)(OR)(OH) consistent with EtOP(S)(O) as an intermediate. In the absence of a trap, 2 was cleanly converted to the pyrophosphate derivative 4 in a process established to follow first-order kinetics, thus proving that decomposition of 2 proceeded by elimination of EtOP(S)(O). Compound 3 decomposed by mixed first and second order kinetics, and gave a more complex mixture of products. EtOP(S)(O) generated from 2 phosphorylated the OH groups on the surface of silica gel, a process previously demonstrated for ROPO₂. With a monoester of phosphoric acid, the mixed monothiopyrophosphate EtOP(S)(OH)-O-P(O)(OH)(OR) was formed in a new synthetic approach to these valuable compounds.     

Preconcentration of lead complexed with O,O-diethyl-dithiophosphate by column solid-phase extraction using different sorbents in a flow injection system coupled to a flame atomic absorption spectrometer

A comparative study of C(18) immobilized on silica, activated carbon and a polyurethane foam, as sorbents for Pb complexed with O,O-diethyl-dithiophosphate in a flow injection preconcentration system is reported. The complex was formed in 1.0 M HCl medium and processed in a simple system using a peristaltic pump, a manual injector-commutator and a mini-column filled with the sorbent. Using ethanol as eluent, the richest 150-mul fraction was collected and measured (after discarding 150, 200 and 0 mul for the activated carbon, foam and C(18), respectively) by flame atomic absorption spectrometry. The optimum concentration of the complexing agent was 0.05% m/v for C(18) and 0.2% m/v for the activated carbon and the polyurethane foam. The best sample loading flow rate was 4.0 ml min(-1) for the activated carbon and 2.0 ml min(-1) for C(18) and the polyurethane foam, while the best elution flow rate was 1.0 ml min(-1) (activated carbon) and 0.6 ml min(-1) (C(18) and foam). It was found that beyond a certain loading sample volume, for a constant analyte mass, the signal decreased. The maximum loading sample volume, for a constant analyte mass, before the signal started to decrease, was 50 ml for the activated carbon and 150 ml for the other materials. By processing 25 ml, the enrichment factors were 23, 55 and 166 for the activated carbon, foam and C(18), respectively. The best limit of detection (3sigma) was 0.3 mug l(-1) for the C(18) (1.2 mug l(-1) for the foam and 3 mug l(-1) for the activated carbon). As shown, the C(18) has a much superior retention performance in comparison to the other two materials.