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Asymmetric alkyl phospholanes have been diastereoselectively synthesized by addition of an unsymmetrical bis-Grignard reagent and of a mono-Grignard reagent to benzothiadiphosphole (1) and isolated as sulfides. The relative cis/trans ratio of the products depends on the steric hindrance of the mono-Grignard used. An accurate analysis of NMR and stereoselective data revealed the fundamental role played by hexacoordinated phosphorus intermediates in driving the stereochemical outcome of the reaction. The particular bicyclic and folded structure of reagent 1 strongly stabilizes hypercoordinated phosphorus species involved in the reaction and favors their formation. Pentacoordinate and metastable hexacoordinate phosphorus species have been detected and their evolution studied through (31)P NMR spectroscopy. The diastereoselective outcome of the reaction between reagent 1 and the couple bis-Grignard reagent 5/mono-Grignard reagent has been explained through a pathway involving hexacoordination of the phosphorus as a key step.

The reaction of 1,2-diaza-1,3-butadienes with dibenzyl diisopropylphosphoramidite, methyl tetraisopropylphosphorodiamidite or tris(dimethylamino)phosphane under solvent-free conditions gave stable α-phosphoranylidene-hydrazones that, in turn, were transformed into the corresponding 5-oxo-4-phosphoranylidene-4,5-dihydro-1H-pyrazoles. X-ray diffraction analysis of one of these derivatives is reported. α-Phosphoranylidene-hydrazones, derived from the reaction between 1,2-diaza-1,3-butadienes with dibenzyl diisopropylphosphoramidite, were converted by hydrolytic cleavage into (E)-hydrazono-phosphonates, which are useful for the preparation of the corresponding (3-oxo-2,3-dihydro-1H-pyrazol-4-yl)phosphonamidates.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

The reaction of benzothiadiphosphole 1 with an equimolar mixture of R 1 MgBr and R 2 MgBr gave intermediate A¢, which, after only 4-5 min, was treated with an equimolar amount of R 3 MgBr, giving the asymmetric phosphine PR 1 R 2 R 3 in 45% overall yield (75-80% yield when R 1 ) R 2 and 85-90% yield when R 1 ) R 2 ) R 3 ) and the byproduct 6 in 90% yield. The treatment of 6 with PCl3 quantitatively regenerates the starting reagent 1. Treatment of the phosphines with elemental sulfur gave the corresponding sulfides.

The use of a PCl3/hydrazone/dicarboxylic acid combination can be applied in an efficient one-pot procedure for the synthesis at room temperature of the title ring compounds that are also a new family of stable enamines. The phthalazinediones 7 were obtained in good yields by reaction of PCl3 with phthalic acid and hydrazones 1a,b,c containing hydrogen atoms only in one α position. Two structurally isomeric phthalazinediones (7 and 8) were obtained with hydrazones 1d,e,f,g containing hydrogen atoms in the two different α positions. When we used a methyl ketone hydrazone 1c,d,e,f,i, it was possible also to isolate the isomer containing an N-alkenyl group with two terminal hydrogen atoms. Where E,Z isomers are possible, the exclusive formation of the E isomer was always observed. As a rule, changing the order of addition of reagents gave almost identical results; however, in the case of phthalic acid, it is better to use the procedure in which PCl3 is added last to prevent the formation of the corresponding anhydride. © 1999 John Wiley & Sons, Inc. Heteroatom Chem 10: 291–296, 1999

A fresh look has been taken at the reaction of PCl3 with thioanisole 1b and AlCl3 that gives, after treatment with water, the title compounds cis-2b in 38% yield together with small amounts of the isomeric cis-3b (2%). The course of this reaction has been studied by 31P-NMR spectroscopy. A multistep pathway, governed by the formation of several AlCl3 complexes with sulfur and phosphorus containing intermediates, has been proposed. The crucial step of this reaction is very reasonably an intramolecular electrocyclic ring closure of a diphosphane intermediate. From this plausible mechanism, an improved procedure that gives only the cis-2b isomer in 42% yield has been realized. In addition, an alternative synthesis using p-thiocresol that gives compounds cis-2b and cis-3b in a ratio of about 2:1 has been effected. © 1997 John Wiley & Sons, Inc. Heteroatom Chem 8:551–556, 1997

A series of glycoluril derivatives have been synthesized in water at room temperature from urea and 1,2-dicarbonyl compounds in the presence of phosphoric anhydride. The reaction time is about 10 minutes using one mole of 1,2-dicarbonyl compound, three moles of urea, and half mole of P4O10, but the reaction occurs also, even if with longer reaction times, with very small amounts of P4O10 which is recovered at the end of reactions. In fact, several catalytic turnovers can be performed using the same reaction solution obtained after separation by simple filtration of the glycolurils.

Fused 1,3-benzothiaphospholes 2 (cis-2,6,10-trimethyl-[1, 3]benzothiaphospholo[2,3-b][1, 3]benzothiaphosphole) reacts with H2O2 and S8, giving the corresponding oxide and sulfide, respectively. The reactions of 2 with diethyl azodicarboxylate (DEAD)/catechol or DEAD/o-aminophenol, o-azidophenol, and tetrachloro-o-benzoquinone (TOB) give the first examples of spiro pentacoordinated phosphorus derivatives of this heterocyclic system. The X-ray structural analysis of spiro compound 3 showed a trigonal bipyramidal configuration at phosphorus in which the three rings assume axial-equatorial positions.

Phospha-Michael additions of a series of methylene-bridged phosphorus bidentate nucleophiles to 1,2-diaza-1,3-dienes gave monoadducts and bisadducts in high yields under mild conditions. In particular, a series of new ylides and symmetrical diylides have been obtained from bis(diphenyl)phosphanes. The use of diphenylphosphanylamino derivatives gave, through phospha-Michael addition, ylide intermediates that underwent spontaneous intramolecular attack by the amino group belonging to the Michael donor reagent moiety, thus giving access to new heterocycles.

New derivatives of 1,2-dihydro-2-alkenyl-3H-pyrazol-3-ones 6 and 7 have been synthesized at room temperature by a one-pot two-step reaction of PCl3, a ketone methylhydrazone, and a β-keto ester. With ketone methylhydrazones bearing at least a phenyl group in the α-positions to the CN bond and in the second step β-keto esters, such as propionyl- or butyrylacetates, we obtained 2-pyrrolylacetates 8 as unexpected products together with pyrazolones 7. The ratio of the two products depends on the nature of the groups in the α-positon to the CN bond. A chlorodiazaphospholine 1 is the key intermediate of this new reaction, and a plausible mechanism of formation of the azaheterocycles is reported.

The title compound 2b was obtained as a minor product in the reaction between a thioanisole and PCl3/AlCl3. The crystal and molecular structure has been determined by single crystal X-ray techniques. The compound crystallizes in the space group P 21/c, with α = 9.004(2), b = 13.416(3), c = 11.662(3) A, and β = 93.1 (1)°. The molecule adoptes a “butterfly” arrangement.

4-Bromodiazaphosphole-3-oxides or sulfides can be obtained by reaction of the corresponding unsubstituted derivative with appropriate reagents. PTAB was demonstrated to be very regio- and stereoselective, allowing bromination exclusively at the 4-position of the ring with prevalent or exclusive formation of one of the two possible isomers. However, when regioselectivity is not required, cheaper and more available bromine or NBS can be used conveniently. 4-Chlorodiazaphosphole-3-oxides can be obtained by reaction of the corresponding unsubstituted derivative with NCS. 4-Bromodiazaphosphole-3-oxides undergo stereoselective methanolysis as well as parent unsubstituted oxides.

Phosphorus-31 NMR static powder spectra and high-resolution magic angle spinning spectra have been obtained for a new heterocyclic compound, cis-2,10-dimethyl[1,2,3]benzothiadiphospholo[2,3b][1,2,3]benzothiadiphosphole (1), which contains a P(III)—P(III) single bond. The homonuclear 31P–31P dipolar interaction manifests itself in both the magic angle spinning spectra and the non-spinning line shape. Under the AX spin pair approximation, analysis of the spinning sidebands in the MAS experiment yields a full characterization of the two 31P chemical shielding tensors. This approximation is confirmed by the exact powder line shape simulation for a homonuclear spin pair. Analysis of the dipolar subspectra also yields the absolute sign of 1J(P,P), which is found to be negative. Keywords: phosphorus–phosphorus single bond, chemical shielding tensors, dipolar NMR, MAS, static line shape.

The reaction of 1,2-diaza-1,3-butadienes with dialkyl phenylphosphonites under solvent-free conditions proceeds via zwitterionic intermediate and gives, by precipitation, the stable ylidic α-phosphanylidene-hydrazones that, in turn, can be transformed into the corresponding 3-phenyl-2 H -1,2,3λ 5 -diazaphospholes. The latter compounds are converted by hydrolytic cleavage in methanol–water (95:5) into E -hydrazonophosphonates that are useful for the preparation of the corresponding β-ketophosphonates and 4-[alkoxy(phenyl)phosphoryl]-1,2-diaza-1,3-butadienes. These peculiar 1,2-diaza-1,3-butadienes, bearing an alkoxy(phenyl)phosphoryl group on the carbon atom in position 4 are also able to add different nucleophiles, such as methanol or thiourea, giving 2-[alkoxy(phenyl)phosphoryl]-2-methoxyhydrazones and 5-phosphinate-substituted thiazol-4-ones, respectively.

Treatment, at room temperature, of benzothiadiphosphole 1 with BrMg(CH2)5MgBr gives intermediate A, which was allowed to stand for about 3 h at room temperature. The subsequent addition of RMgX to the reaction mixture and the final treatment with an excess of S8 and water affords the dithiaphosphepine sulfide 8 in good yields. The structure of this new heterocyclic system, containing both an SS unit and a PS group, is confirmed by an single crystal X-ray structure determination. If the reaction is carried out without final treatment with sulfur we obtain, using PhMgBr as mono-Grignard reagent, the corresponding ring-opened product 11b, which can be easily transformed into the corresponding ring-opened sulfide 12b by simple treatment with elemental sulfur. Further addition of sulfur to 12b gives quantitatively the cyclic dithiaphosphepine sulfide 8b. The two phosphanethiols 11b and 12b are of considerable interest. In fact, recently, attention has increasingly been paid to the coordination chemistry of polydentate ligands incorporating both thiolate and tertiary phosphine groups, also known as SPS pincer ligands. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:339–345, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20099

[structures: see text] The present article describes the reaction between 1,2-diaza-1,3-butadienes and trialkyl phosphites, under an atmosphere of nitrogen and under solvent-free conditions, to give alkyl 3,3-dialkoxy-2H-1,2,3lambda5-diazaphosphole-4-carboxylates that, in turn, are converted into corresponding E-hydrazonophosphonates by treatment with THF:water (95:5). These latter compounds are obtained directly by the reaction of 1,2-diaza-1,3-butadienes with trialkyl phosphites in the presence of air. These compounds are useful for the further preparation of dialkyl (5-methyl-3-oxo-2,3-dihydro-1H-4-pyrazolyl)phosphonates and 2-dialkoxyphosphoryl-1,2,3-thiadiazoles.

The use of the PCl3/hydrazone/dicarboxylic acid combination can be applied in an efficient one-pot procedure for the synthesis at room temperature of the seven-membered ring compounds, 6 (perhydro-1,4,5-oxadiazepine-3,6-diones) and 7 (perhydro-1,4,5-thiadiazepine-3,6-diones), and of the first reported derivatives of the heterocycle 6,7-diazaspiro[3.4]octane-5,8-dione 8. Compounds 6 and 7, containing an N-alkenyl group, were obtained in good yields using diglycolic and thiadiglycolic acids with PCl3 and methylhydrazone 1, with use of a high concentration (0.5 M) of the reagents. N-alkenyl derivatives 8 were obtained in the same manner using 1,1-cyclobutanedicarboxylic acid. Changing the order of addition of the reagents gave almost identical results. In the case in which the exocyclic double bond can give E,Z-isomers, the exclusive or prevalent formation of the E-isomer was always observed. © 1999 John Wiley & Sons, Inc. Heteroatom Chem 10:615–621, 1999