A novel synthesis of α,β-unsaturated phosphonates

A stereoselective synthesis of α,β-unsaturated phosphonates based on the reaction of S-(β-oxoalkyl)-dithiophosphates and Se-(β-oxoalkyl)selenophosphates with sodium dialkyl phosphites is described.     

Stereocomplex formation between enantiomeric poly(α‐methyl‐α‐ethyl‐β‐propiolactones): Effect of molecular weight

Optically pure S(?) and R(+)‐poly(α‐methyl‐α‐ethyl‐β‐propiolactones) (PMEPLs) of controlled low molecular weights were synthesized by anionic polymerization of the corresponding optically active monomers, and characterized using gel permeation chromatography, Maldi‐TOF mass spectrometry, and NMR spectroscopy. Blends of PMEPLs of opposite configurations and different molecular weights were investigated. All blends lead to the formation of a stereocomplex and its crystallization prevails over a wide range of mixing ratios. The stereocomplex melts 30–40 °C above that of the corresponding pure polymers, depending on the molecular weight; pairs of polymers having similar molecular weights exhibit the highest melting temperatures and enthalpies of fusion. Finally, when the stereocomplex is dispersed in a PMEPL matrix, it acts as a very effective nucleation agent for the crystallization of the polymer in excess. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2380–2389, 2007     

Synthesis of Functionalized Novel α‐Amino‐β‐alkoxyphosphonates through Regioselective Ring Opening of Aziridine‐2‐phosphonates

Aziridines are highly useful compounds as building blocks for the synthesis of important organic compounds. Amino acid synthesis by aziridine ring opening reaction is a good example to the use of aziridines. Although this reaction is studied by many groups, the synthesis of amino phosphonic acids is less explored. In this study, we have carried out the ring opening reaction of aziridinyl phosphonates with a variety of alcohols including the more functional propargylic and allylic alcohols. These reactions provided functionalized α‐amino‐β‐alkoxyphosphonates in 40–91 % yield.     

Two members of the bis­phospho­nate class of drugs: a zwitterion and a molecular compound

The compounds studied in this paper, viz. (1‐ammonio‐1‐phosphono­propyl)­phospho­nate, C₃H₁₁NO₆P₂, (I), and 1‐(acetyl­amino)­propyl­idene‐1,1‐bis­phospho­nic acid dihydrate, C₅H₁₃NO₇P₂·2H₂O, (II), are members of a commonly used family of therapeutic agents. Compound (I) is an inner salt with separated negative (on the ionized PO₃ group) and positive (on the tetrahedral N atom) charges, while (II) possesses neutral phospho­nyl groups and one amide N atom. Both structures have a C—C—C—N backbone, which has comparable geometric parameters in (I) and (II); the main difference was found in one of the N—C—P bond angles, which is lengthened in (II) because of an intramolecular O_PO3—H⃛O_C=O interaction. The hydrogen‐bonding scheme in the crystal of (I) includes all possible donor atoms, namely all the H atoms of the ammonium group and the phospho­nic acid functions. As a result of these interactions, the zwitterions are organized into a plane running along the crystallographic x axis. In (II), the intermolecular interactions include all possible donor atoms, except for the N atom; the packing differs from that of (I) in that the mol­ecules are arranged in a chain running parallel to the x axis. In the chains, the mol­ecules form head‐to‐head dimers, while the crystallization water mol­ecules contribute to the intra‐ and interchain cohesion.     

Stereodivergent Dual Catalytic α‐Allylation of Protected α‐Amino‐ and α‐Hydroxyacetaldehydes

Fully stereodivergent dual‐catalytic α‐allylation of protected α‐amino‐ and α‐hydroxyacetaldehydes is achieved through iridium‐ and amine‐catalyzed substitution of racemic allylic alcohols with chiral enamines generated in situ. The operationally simple method furnishes useful aldehyde building blocks in good yields, more than 99 % ee, and with d.r. values greater than 20:1 in some cases. Additionally, the γ,δ‐unsaturated products can be further functionalized in a stereodivergent fashion with high selectivity and with preservation of stereochemical integrity at the C_α position.     

α,α‐Dibromotoluene as a monomer for poly (substituted methylene) synthesis: Magnesium‐mediated polycondensation of α,α‐dibromotoluene and magnesium/copper‐mediated copolycondensation of α,α‐dibromotoluene with 1,6‐dibromohexane

α,α‐Dibromotoluene 1 was found to be polymerized by the reaction with excess Mg to give poly(phenylmethylene)s 2 , whose main chains were partially dehydrogenated to carbon–carbon double bonds (C?C). The C?Cs in 2 can be brominated by treatment with Br₂. The polymerization mechanism was presumed to include the formation of Grignard reagents of various species with benzylic C? Br bonds and the nucleophilic attacks of the Grignard reagents to various compounds with benzylic C? Br bonds. Copolymerization of 1 with dichlorodimethylsilane successfully proceeded. Mg/Cu‐mediated copolycondensation of 1 with 1,6‐dibromohexane proceeded to give polymers that have similar compositions to those of random copolymers of ethylene and styrene. © 2006Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5661–5671, 2006     

Facile one‐pot synthesis of α‐amino phosphonates using lanthanide chloride as catalyst

An efficient preparation of α‐amino phosphonates by the one‐pot condensation of aldehydes, amines, and dialkyl phosphites using catalytic amounts of lanthanide chloride under mild conditions is successfully developed. Moreover, the catalyst is water‐tolerant and could be recovered and reused. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:389–392, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20219     

Concise Synthesis of α‐Methylene‐β‐hydroxy‐γ‐carboxy‐γ‐lactams

A concise protocol for the synthesis of α‐methylene‐β‐hydroxy‐γ‐carboxy‐γ‐lactams has been described via alkylation of amino acid derived iminoesters with α‐bromomethylmethacrylate, followed by allylic hydroxylation. All the synthesized compounds have been evaluated for their cytotoxicity on multiple myeloma cancer cell lines.     

Photoredox Catalytic α‐Alkoxypentafluorosulfanylation of α‐Methyl‐ and α‐Phenylstyrene Using SF6

SF₆ was applied as pentafluorosulfanylation reagent to prepare ethers with a vicinal SF₅ substituent through a one‐step method involving photoredox catalysis. This method shows a broad substrate scope with respect to applicable alcohols for the conversion of α‐methyl and α‐phenyl styrenes. The products bear a new structural motif with two functional groups installed in one step. The alkoxy group allows elimination and azidation as further transformations into valuable pentafluorosulfanylated compounds. These results confirm that non‐toxic SF₆ is a useful SF₅ transfer reagent if properly activated by photoredox catalysis, and toxic reagents are completely avoided. In combination with light as an energy source, a high level of sustainability is achieved. Through this method, the proposed potential of the SF₅ substituent in medicinal chemistry, agrochemistry, and materials chemistry may be exploited in the future.     

17‐Oxo‐5α‐androstane‐3α,4β‐diyl diacetate and 17‐oxo‐5β‐androstane‐3α,4β‐diyl diacetate

The title compounds, both C₂₃H₃₄O₅, are the 5α and 5β configurations of two diacetate epimers. The 5β‐diacetate crystallizes in an hexagonal structure, unusual for steroid molecules. The unit cell has an accessible solvent volume of 358 ų, responsible for clathrate behaviour. The 5β‐epimer also features some shorter than average bond lengths in the 3α,4β‐acetoxy groups. The conformations of the molecules of both epimers are compared with those obtained through abinitio quantum chemistry calculations. Cohesion of the crystals can be attributed to van der Waals and weak molecular C—H⋯O interactions.     

Two N‐ortho‐nitro­benzene­sulfonyl α,α‐disubstituted amino acid adducts

The carboxy group of 2‐methyl‐N‐[(2‐nitrophenyl)sulfonyl]­alanine, C₁₀H₁₂N₂O₆S, forms centrosymmetric hydrogen‐bonded dimers with an O?O distance of 2.629 (2) Å and an intramolecular N—H?O(nitro) hydrogen bond N?O distance of 2.823 (2) Å. 1‐[(2‐Nitro­phenyl)­sulfonyl­amino]­cyclo­hexane­carboxyl­ic acid, C₁₃H₁₆N₂O₆S, has Z′ = 2 and forms similar interactions.     

Efficient Synthesis of α‐Benzylidene‐γ‐methyl‐γ‐butyrolactones

A concise synthesis of α‐benzylidene‐γ‐methyl‐γ‐butyrolactones 5a – g from substituted benzaldehydes is described. Compounds 1a – g on reaction with phosphorane 2 , provide the pentenoates 3a – g , which can be hydrolyzed to the acids 4a – g . The latter are cyclized to the corresponding butyrolactones 5a – g in excellent yields. The pentenoates 3a – g , on acid catalyzed cyclization, also provide 5a – g in very high yields.