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Two novel heterocyclic dienes, 2-ethoxy-3-phenyl-2 H -oxo-1,2-oxaphosphorin 2-oxide ( 3 ) and 5-bromo-2-ethoxy-3-phenyl-2 H -oxo-1,2-oxaphosphorin 2-oxide ( 4 ), are described. They were prepared in four steps starting from 2-ethoxy-3-phenyl-1,2-oxaphosphorinane 2-oxide ( 12a , b ) ( trans and cis ) by a bromination–dehydrobromination sequence. Free radical bromination of 12a , b with NBS/AIBN furnished two isomeric bromides 13a , b . Isomer 13b gave 2-ethoxy-5,6-dihydro-3-phenyl-2 H -1,2-oxaphosphorin 2-oxide ( 14 ) on treatment with LiCl/DMF. Isomer 13a underwent COEt bond cleavage followed by HBr elimination to give the phosphonic acid 17 . Treatment of 14 with NBS/AIBN afforded isomeric 5-bromo-2-ethoxy-5,6-dihydro-3-phenyl-2 H -1,2-oxaphosphorin 2-oxides ( 15a , b ) and 5,5-dibromo-2-ethoxy-5,6-dihydro-3-phenyl-2 H -1,2-oxaphosphorin 2-oxide ( 18 ), separated by chromatography. Dehydrobromination of 15a , b , and 18 with an excess of Et 3 N in toluene at 80–95 °C provided the target dienes 3 and 4 , respectively. more...

The parent phostone, 2-ethoxy-1,2-oxaphosphorinane 2-oxide 1, and derivatives with substituents at the 3-position (methyl, phenyl, and benzyl; compounds 2-4) were converted with Lawesson's reagent to provide the corresponding sulfide analogues 5-8 in moderate yields. The conversion of 2-4 occurred with retention of configuration at the phosphorus center. This was implied from the relative Rf values and 13C and 31P NMR chemical shifts of the individual isomers and confirmed for the transformation of 3b to 7b by X-ray structures of each of these. Oxidation of 7b, 8a, and 8b with m-chloroperoxybenzoic acid alone led to the corresponding oxides 3b, 4a, and 4b with retention. The presence of trifluoroacetic acid during this oxidation process led to varying degrees of epimerization about phosphorus and was dependent on the relative molar equivalents of this acid.Key words: 2-ethoxy-1,2-oxaphosphorinane 2-oxide, 2-ethoxy-1,2-oxaphosphorinane 2-sulfide, phostone, thiophostone, Lawesson's reagent, stereoselective synthesis, X-ray diffraction. more...

The solid state structures of three phosphorus heterocycles trans- and cis-4-methyl-4-phosphatetracyclo [3.3.0.02,8.03,6]octane 4-sulfide (3a and 3b, respectively) and trans-4-phenyl-4-phosphatetracyclo[3.3.0.02,8.03,6]octane 4-oxide (5a), were established by X-ray crystallography. Although the ring structure in each was expected to be conformationally rigid, some differences were noted when 3a, 3b, 5a, and 4- methyl-4-p-nitrobenzyl-4-phosphoniatetracyclo[3.3.0.02,8.03,6]octane bromide (4) were compared. Examination of both bond lengths and angles indicates that the phosphetane ring is greatly affected by the tetracyclic system. Semi-empirical calculations at the PM3 level were used to estimate the relative energy of cis and trans 5. The single crystal data are as follows: (trans-3a), triclinic, P-1, with a = 6.2227(4) A,b = 6.5205(6) A, c = 10.3651(13) A, α = 86.670(10)°, β = 87.340(8)°, γ = 83.712(6)°, V = 416.99(7) A3, Z = 2, D calc = 1.356 g/cm3, 743 observed reflections, and R = 0.040; (cis-3b), tric... more...

The secondary phosphonate ester endo-2-(diethoxyphosphoryl)bicyclo[2.2.1]heptane 6 was prepared in stereoselective fashion for the first time by hydrogenation of 2-(diethoxyphosphoryl)bicyclo[2.2.1... more...

The secondary phosphonate ester exo-2-(dimethoxyphosphoryl)bicyclo[2.2.1]heptane 1 was prepared by literature methods on a mole scale. This synthetic method was extended to include the stereoselective preparation of the exo-diethyl phosphonate analog 3 in 71% yield. Derivatization of these exo-phos-phonates 1 and 3 required vigorous conditions, but proceeded in moderate to high yields. The configuration about carbon-2 was retained in all but one case. Isomerization about carbon-2 was observed during the desulfurization of exo-thiophosphonic dichloride 15 with triphenylphosphine at 240°C. A 3:2 ratio of exo- to endo-phosphonous dichlorides 16 resulted. When the reaction was conducted at 100°C, exo-phosphonous dichloride 16 was formed without epimerization at carbon-2 (97% exo isomer). The exo-dichloride 16 isomerized to the endo-isomer upon treatment with triphenylphosphine at 240–260°C. The intermediate phosphaalkene 17 was implicated to precede this isomerization. Moreover, intentional isomeriza... more...

The crystal structure of the title compound, diphenyl 1-hydroxy-1-phenylethylphosphonate (1), was determined by the single-crystal X-ray diffraction method. The crystallographic data for 1 are as follow: C20H19O4P, Mr = 354.34, monoclinic, P21/n, a = 9.787(1) A, b = 20.235(1) A, c = 9.797(1) A, β = 106.18(3)°, V = 1863.3(4) A3, Z = 4, Dcalc = 1.26 g/cm3, λ(Mo-Ka) = 0.71073 A, μ = 1.6 cm−1, F(000) = 744, R = 0.018, and Rw = 0.032 for 2258 observed reflections. The solid-state structure in a dimeric packing mode exhibits intermolecular hydrogen bonding of the type P = O···H–O. Infrared solution studies (CCl4) indicate that upon high dilution (10−4 M) the dimers completely dissociate to give conformers with and without intramolecular hydrogen bonds. Theoretical studies (PM3) were undertaken to determine the energy profile about the P–C torsional angle, which exhibited low energy barriers to rotation with no clear minimum energy conformation. © 1996 John Wiley & Sons, Inc. more...

Three derivatives of the parent 4-tert-butylphosphorinane sulfide were prepared and investigated by single crystal X-ray diffraction: trans-4-tert-butyl-1-phenoxyphosphorinane sulfide (2a) and the cis and trans isomers of 4-tert-butyl-1-phenylphosphorinane sulfide (3b and 3a, respectively). Crystallographic data for 2a: space group P21/n (No. 14) with a = 6.1670(6) A, b = 10.999(1) A, c = 23.275(2) A, β = 94.978(7)°, V = 1572.7(5) A3, and Dcalc = 1.193 g cm−3 for Z = 4, R = 0.040; for 3a: space group C2/c (No. 15) with a = 25.826(3) A, b = 6.427(1) A, c = 20.050(3) A, β = 111.57(1)°, V = 3094(1) A3, and Dcalc = 1.143 g cm−3 for Z = 8, R = 0.043; for 3b: space group P21/c (No. 14) with a = 6.2914(7) A, b = 11.632(1) A, c = 21.088(1) A, β = 96.892(7)°, V = 1532.1(4) A3, and Dcalc = 1.155 g cm−3 for Z = 4, R = 0.048. In every structure the phosphorinane ring adopts a chair conformation with tert-butyl group in an equatorial position. The relative spatial arrangement of the latter and the phenoxy or ... more...

The molecular structures of both the cis(4a) and trans(4b) isomers of 3-(diphenylhydroxymethyl)-2-ethoxy-2-oxo-1,2-oxaphosphorinane were determined by the single crystal X-ray diffraction method. The cis and trans designation refer to the relative spacial arrangements of the phosphoryl oxygen and the substituent group on the α-carbon. The crystallographic data are for 4a: C19H23O4P, Mr = 346.36 monoclinic, P21/c, a = 13.2774(9) A, b = 8.5543(9) A, c = 16.7289(25) A, β = 111.142(10)°, V = 1772.2(4) A3, Z = 4, Dcalc = 1.298 g cm−3, λ(MoKα) = 0.71069 A, μ = 1.70 cm−1, F(000) = 736, T = 298 K, R = 0.065 for 2099 reflections; and for 4b: C19H23O4P, Mr = 346.36, monoclinic, P21/c, a = 9.5120(15) A, b = 12.317(4) A, c = 15.309(3) A, β = 100.717(15)°, V = 1762.3(7) A3, Z = 4, Dcalc = 1.305 g cm−3, μ(MoKα) = 0.71069 A, μ = 1.60 cm−1, F(000) = 736, T = 298 K, R = 0.041 for 1638 reflections. In both structures the diphenylhydroxymethyl group is in an equatorial position, and the 1,2-oxaphosphorinane ring ad... more...

Improved methods for the synthesis of 5- and 6-membered ring phostones 2 and 1 as well as original preparations of bicyclic phostones 4 (n=1,2) have been successfully executed. The preparation of the 4-membered ring 3 was more elusive, but the observed products indicated its presence as an intermediate which underwent further transformations. Reaction of 1 with 2,2,6,6-tetramethylpiperidide at low temperature, followed by treatment with a variety of alkyl halides gave the expected alkylation products whose cis/trans stereochemistry was dependent on the reaction conditions. Subsequent ring closure of the cis or trans alkylated product 10, gave only the cis fused bicyclic product 4. In fact, other synthetic routes to 4 produced only the cis isomer. The mechanisms and stereochemistry of these various conversions will be discussed. more...

Improved methods for the synthesis of 5- and 6-membered ring phostones 2 and 1 as well as original preparations of bicyclic phostones 4 (n=1,2) have been successfully executed. The preparation of the 4-membered ring 3 was more elusive, but the observed products indicated its presence as an intermediate which underwent further transformations. Reaction of 1 with 2,2,6,6-tetramethylpiperidide at low temperature, followed by treatment with a variety of alkyl halides gave the expected alkylation products whose cis/trans stereochemistry was dependent on the reaction conditions. Subsequent ring closure of the cis or trans alkylated product 10, gave only the cis fused bicyclic product 4. In fact, other synthetic routes to 4 produced only the cis isomer. The mechanisms and stereochemistry of these various conversions will be discussed. more...

The parent phostone, 2-ethoxy-1,2-oxaphosphorinane 2-oxide 1, and derivatives with substituents at the 3-position (methyl, phenyl, and benzyl; compounds 2-4) were converted with Lawesson's reagent to provide the corresponding sulfide analogues 5-8 in moderate yields. The conversion of 2-4 occurred with retention of configuration at the phosphorus center. This was implied from the relative Rf values and 13C and 31P NMR chemical shifts of the individual isomers and confirmed for the transformation of 3b to 7b by X-ray structures of each of these. Oxidation of 7b, 8a, and 8b with m-chloroperoxybenzoic acid alone led to the corresponding oxides 3b, 4a, and 4b with retention. The presence of trifluoroacetic acid during this oxidation process led to varying degrees of epimerization about phosphorus and was dependent on the relative molar equivalents of this acid.Key words: 2-ethoxy-1,2-oxaphosphorinane 2-oxide, 2-ethoxy-1,2-oxaphosphorinane 2-sulfide, phostone, thiophostone, Lawesson's reagent, stereoselective ... more...

The title compound crystallizes in the monoclinic space groupP21/a witha=13.092(2) A,b=15.853(2) A,c=15.406(3) A,β=103.00(1)°,V=3116(1) A3, andDcalc=1.237 g cm−3 forZ=4. The structure was solved by direct methods, and refined to a finalR value of 0.057. The phosphetane ligands adopt a nonlinear trans relationship. The four-membered rings are non-planar and have different flap angles of 6.1 and 20.3°. Virtual coupling is evident in the13C NMR spectrum of the title compound. Comparison of the13C NMR spectral data of this molecule with the parent phosphine ligand, the ligand oxide, and the mono-phosphine iron complex is provided. more...

Ring closure of the bis-Grignard derived from cis-1,3-bis(bromomethyl)cyclopentane (5) on R 2 GeCl 2 (R=Ph or Me) afforded a 3-germabicyclo[3.2.1]octane system. Bromine cleavage of a phenyl group in 3,3-diphenyl-3-germabicyclo[3.2.1]octane and subsequent nucleophilic displacement of the bromide allowed differing substitution on the germanium atom. The incorporation of germanium into the bicyclo[2.2.1]heptane system was achieved through a chloroplatinic acid catalyzed, intramolecular hydrogermylation reaction of di-n-butyl(3-cyclopentenylmethyl)germane. The physical and spectral properties of these new molecules are presented more...

C 21 H 26 PBr cristallise dans Pna 2 1 avec a=18,348, b=10,479 et c=10,216 A, Z=4; affinement jusqu'a R=0,056

The crystal structure of the title compound, C 9 H 15 O 5 P, is described. The molecule consists of two cis-fused six-membered rings, both in the chair conformation

Ring closure of the bis-Grignard derived from cis-1,3-bis(bromomethyl)cyclopentane (5) on R 2 GeCl 2 (R=Ph or Me) afforded a 3-germabicyclo[3.2.1]octane system. Bromine cleavage of a phenyl group in 3,3-diphenyl-3-germabicyclo[3.2.1]octane and subsequent nucleophilic displacement of the bromide allowed differing substitution on the germanium atom. The incorporation of germanium into the bicyclo[2.2.1]heptane system was achieved through a chloroplatinic acid catalyzed, intramolecular hydrogermylation reaction of di-n-butyl(3-cyclopentenylmethyl)germane. The physical and spectral properties of these new molecules are presented more...

The purpose of this study was to synthesize trans-l and determine the equilibriurr constant with cis-1. Oniy the synthesis1 and x-ray structure2 of the cis isomer have bcen reported. Four prior synthetic routes to make the vans isomer3 gave only cis product. For example, intrarmolecular ring closure of the cis or trains isomers of 4 (R= (CH2)3OH) with LiH or thermal closure of the cis or trans 4 (R= (CH2)2) gave only cis-1. Since both iosmers of 1,8-dioxabicyclo[4.4.0] decane are known and readily equilibrate (57% cis and 43% trans), the apparent inaccessibility of trans-1 attracted our attention. Thc preparation of trans-1 was achieved by treatment of cis-1 with Lawesson's reagent (LR) to provide cis-2. followed by oxidation with m-chloroperbenzoic acid/trifluoroacetic acid to give a 5:1 mixture of cis:trans 1, respectively. An unexpected formation of the sulfur analogue of 1 was observed on treatment of cis-1 with P2S5/pyridine at reflux temperatures to give a 1.6:1 mixture of cis:trans 3, resp... more...

In view of the limited number of examples of 2-oxo-l,2-oxaphosphorinane3,5diene derivatives1,2, we investigated the preparation of the title compound and derivatives of the same. Of additional interest were the spectroscopic propertits of this class of compounds, their stability, and the outcome of their reaction with nucleophilts. Prior work in our laboratory on the synthesis of simple phostones and their derivatives3, led us to use these as starting mataials. The presence of the phenyl substituent in la, (cis and trans isomers) permitted facile introduction of a bromo group through free radical bromination with NBS/AIBN to give 2a,b in 79% overall yield. The individual isomers of 2 were separated; tentative stereochemical assignments were made using NMR spectroscopy. Treatmnt of 2 with LiCl/DMF gave 3; the trans isomer (phenyl and OEt trans) 2b reacted much faster than the cis isomer. Treatmnt of 3 with NBS/AIBN gave 4a,b and 5 which were separated by flash chromatography. Dehydrobromination of... more...

During our investigations on the wide range of stereoselective alkylations of 6-membered ring phostones,1 we uncovered a novel rearrangement of 3-(diphenylhydroxymethyl)-2-ethoxy-2-oxo-1,2-oxaphosphorinane (1). The cis/trans diastereomers of 1 were prepared by the reaction of benzophenone with the appropriate ylide of the parent phostone (3).2 When trans- 1 was left unattended at rt in CH2Cl2 a new compound, 2, was isolated which showed a significant downfield 31P shift and a higher melting point. Upon heating to the melting point 2 decomposed to give 4, which suggests that 2 may be an intermediate in the conversion of 1 to the Wittig-like product 4. The IR, 1H, 13C, 31P, and 2-D NMR spectral data along with independent synthesis confirmed the identity of 2. Subsequently, 2 was also produced in 70% yield when cis- 1 was treated with CH2Cl2/ether-HC1aq at 50–60°C for 2 weeks, but this product was contaminated with 30% of the exocyclic alkene 5. No rearrangement was observed when 1 was treated with... more...

Although 1,3,2-dioxaphosphorinanes generally assume chair conformations,1 there are examples in which the ring adopts the boat or twist-boat form.1 Recent studies on the synthesis, stereochemistry, and reactivity of 2-alkoxy-2-oxo-1,2-oxaphosphorinanes (phostones) have revealed both cis and trans isomers of 3-(diphenylhydroxymethyl)-2-ethoxy-2-oxo-1,2-axaphosphorinane2 to assume a chair conformation in the solid state. In the present work, the conformational properties of cis and trans-3-methoxycarbonyl-2-methoxy-2-oxo-1,2-oxaphosphorinanes were investigated by X-ray analysis, variable temperature 31P, 1H and 1H{31P} NMR spectroscopy, molecular mechanics, and semiempirical calculations. The X-ray crystal structure of the trans isomer revealed a chair dormation with equatorial phosphoryl and carbomethoxy groups. No changes were observed in the 31P NMR spectra of either isomer in the temperature range of 183–333 K. A complete set of vicinal JHH coupling constants was extracted from the 1H{31P} spec... more...

The conformations of cis- and trans-3-(methoxycarbonyl)-2-methoxy-2-oxo-1,2-oxaphosphorinane have been investigated by variable temperature 31P, 1H and 1H{31P} NMR spectroscopy and semiempirical calculations. An X-ray diffraction study of the trans isomer has also been performed. The 31P NMR spectra of both isomers did not change with temperature over the range of 183–333 K. The temperature dependence of the C(3)–H spectral pattern in the cis isomer suggested an important change in the conformer distribution with temperature. For the trans isomer, no changes were detected. The crystal structure of trans-3-(methoxycarbonyl)-2-methoxy-2-oxo-1,2-oxaphosphorinane was solved by direct methods and refined to R= 0.046. The space group is P21/n, a= 8.644(1), b= 7.432(1), c= 15.718(2)A, β= 105.38(1)°. The molecule in the asymmetric unit adopted a chair conformation with equatorial phosphoryl and methoxycarbonyl groups. The conformation in the crystal agreed well with the calculated global energy minimum conformation. more...

The title compound which we1 and others2 have previously synthesized has now been extensively investigated. The tetracyclic phosphonium chloride 1 was prepared by treatment of norbornadiene with CH3PCl2 at 65–80°C for one week. Treatment of 1 with AICl3/CH2CI2 gave 2. Direct or “Inverse” addition at water to 2 dictated the stereochemistry of the oxide 3. Stereoassignments of 3 were made based on lanthanide shift −1H and 13C nmr studies studies. Extensive 2-D nmr studies (HETCOR, COSY) and triple irradiation experiments enabled chemical shift and coupling constant assignments. more...

The exo/endo isomers of the title compound can be obtained as an equilibrium mixture when treated with cesium fluoride in DMF; the observed equilibrium constant is in agreement with theoretical calculations. more...

The title compound crystallizes in the orthorhombic space groupPna21, witha=15.576(2),b=19.134(3),c=5.693(1) A andz=4. The structure was solved by direct methods, and refined to a finalR value of 0.059. This study confirms both the structure and stereochemistry of the title compound. more...

The title compound crystallizes in the monoclinic space groupP21/n, witha=8.881(1),b=17.718(1),c=13.077(8) A,β=99.17(2)° andZ=4. The structure was solved by the heavy-atom method and refined to a finalR value of 0.059. The four-membered ring is nonplanar, with a puckering angle of 22.0°. The Br and phenyl are in pseudoaxial positions and aretrans to each other in the solid state. more...

The molecular structures of 3-silabicyclo(3.2.1)octane (SB3210) and endo-3-methyl-3-silabicyclo(3.2.1)octane (endo-MSB3210) have been determined by gas phase electron diffraction. The average SiC bond lengths, 1.891(4) A for SB3210 and 1.883(3) A for endo-MSB3210, are comparable with the observed SiC bond lengths in silacyclohexane and silacyclopentane. The average CC bond lengths, 1.552(2) A for SB3210 and 1.548(2) A for endo-MSB3210, also compare favorably with the corresponding distances in silacyclopentane and silacyclohexane. Observed flap angles at the silicon atom are 145(4)° in SB3210 and 160(5)° in endo-MSB3210. Both molecules exhibit considerable flattening at the silicon end of the six-membered ring relative to silacyclohexane which has a flap angle of 139°. The observed structures are compared with the results of molecular mechanics calculations, and with experimental structures for several related compounds. more...

Cesium fluoride isomerization of several derivatives of 3-silabicyclo[3.2.1]octane and 2-silabicyclo[2.2.1]heptane as well as chiral α-NpPhMeSiH are described. The effect of solvent, 18-crown-6 ether, and other salts is discussed. Associated side reactions prompted study of the conversion of Ph3SiH to Ph3SiF by CsF and the identification of the products formed from the reaction of Ph3SiH with DMF, N-methylformanilide, and benzamide in the presence of metal fluorides. more...

The title compounds and their derivatives have been prepared in good yield. Several of the synthetic steps are novel and have general applicability. Isomer assignments for these materials were based upon nmr and x-ray data. A two bond phosphorus-carbon coupling Karplus relation has been established for phosphines and applied to the systems under investigation. Extensive stereochemical studies were conducted. The conformational energy barrier in cis-“phosphadecalin” (2) was estimated to be 12.3–13.6 kcal/mol. Hydroxide ion attack on cis-phosphonium salt 5 went with retention at phosphorus, while cis or trans 4 proceeded with considerable inversion. Nucleophilic displacements on derivatives of phosphorinane generally went with inversion of configuration. more...

The title compound crystallizes in the monoclinic space groupP21/n,a=13.429(3),b=18.248(6),c=14.497(4)A,β=90.61(2)°,Z=8, with two independent molecules in the asymmetric unit. The structure was solved by heavy-atom methods, and refined to a finalR value of 0.040. The phosphoranium ring adopts a chair conformation which is substantially flattened at the phosphorus end. The ring conformation and torsion angles are compared with similar compounds. more...

Carbon-13 spin-lattice relaxation times have been determined for a series of substituted 2,2,3,4,4-pentamethylphosphetanes (four-membered phosphorus heterocycles), including phosphetanes, phosphetanium salts and phosphetane oxides. Nonprotonated carbons have T 1 values of the order of 8–18 sec while protonated carbons have values ranging from 0.6 to 4.0 sec. The rigidity and, in most cases, isotropic nature of the phosphetanes has allowed comparison of T 1 's and subsequent determination of relaxation mechanisms and probing of the ease of internal rotation for each of the several methyl groups on the basic ring backbone. Situations are observed where pseudoequatorial methyl carbons on C-2 and C-4 have relaxation times shorter than those of the presumably more hindered pseudoaxial methyls attached to the same C-2 and C-4 carbons. This points out the danger of directly equating short T 1 values with steric crowding. more...

Cristallisation dans le systeme monoclinique, groupe P2 1 et affinement de la structure jusqu'a R=0,033. Gauchissement du cycle a 4 chainons