Effect of base on alkyltriphenylphosphonium salts in polar aprotic solvents

2008 ◽  
Vol 86 (7) ◽  
pp. 668-675 ◽  
Author(s):  
Julius N Ngwendson ◽  
Cassandra M Schultze ◽  
Jordan W Bollinger ◽  
Anamitro Banerjee
Keyword(s):  
Phosphonium Salt ◽  
Phenyl Group ◽  
Aprotic Solvents ◽  
Phosphonium Salts ◽  
Bromide Form ◽  
Mechanistic Investigation ◽  
High Yields ◽  
Excess Base ◽  
Homocoupling Reaction ◽  
Very High

When arylmethyl phosphonium salts are treated with a base (e.g., t-BuOK or NaH) they homocouple to form symmetric 1,2-diarylethenes. In some cases, dilution and (or) use of excess base lead to very high yields of the product. This reaction is solvent sensitive: the reaction occurs only when polar aprotic solvents such as acetonitrile or DMSO are used. Other alkyl phosphonium salts (e.g., ethoxycarbonylmethyltriphenylphosphonium bromide and n-butyltriphenylphosphonium bromide) form a ylid (when an α-carbonyl group is present) or lose a phenyl group to form alkyldiphenylphosphine oxides when treated with the base. Mechanistic investigation of the homocoupling reaction indicates that the reaction proceeds through a ylid that acts as a nucleophile on an unreacted phosphonium salt. The resulting adduct undergoes elimination to form the observed product. The E/Z ratio seems to depend on the amount of the base used and the phosphonium salt involved.Key words: phosphonium salts, homocoupling, 1,2-diarylalkene, Ylids.

1H and 13C NMR spectra of 2,2’-disubstitutedtrans-azobenzenes suitable for preparation of metallized azo dyes

1991 ◽  
Vol 56 (10) ◽  
pp. 2160-2168 ◽  
Author(s):  
Josef Jirman
Keyword(s):  
Nmr Spectra ◽  
Electron Pair ◽  
Phenyl Group ◽  
Aprotic Solvents ◽  
1H And 13C Nmr ◽  
Predominant Form ◽  
Rapid Equilibrium ◽  
Dipolar Aprotic Solvents ◽  
Free Electron Pair ◽  
C Nmr

The 1H and 13C NMR spectra have been measured of six trans-azobenzenes substituted at 2 and 2’ positions with substituents favourable for complex formation with a metal (OH, NH2, NHCOCH3, COOH). From the standpoint of NMR such substituted trans-azobenzenes are present in solution in a rapid equilibrium following from rotation around the bond between C-1 of phenyl group and N atom of azo linkage. The predominant form has the substituent in the syn-position with respect to the free electron pair of the nearer azo nitrogen atom. The equilibrium is affected by dipolar aprotic solvents (such as hexadeuteriodimethyl sulfoxide) by decreasing the presence of the predominant form by 1 to 11%.

scholarly journals Multi-curie production of gallium-68 on a biomedical cyclotron and automated radiolabelling of PSMA-11 and DOTATATE

2021 ◽  
Vol 6 (1) ◽  
Author(s):  
Helge Thisgaard ◽  
Joel Kumlin ◽  
Niels Langkjær ◽  
Jansen Chua ◽  
Brian Hook ◽  
...  
Keyword(s):  
Radiochemical Purity ◽  
High Yield ◽  
Clinical Use ◽  
Automated Production ◽  
Automated Method ◽  
Gallium 68 ◽  
High Yields ◽  
High Level ◽  
Mev Protons ◽  
Very High

Abstract Background With increasing clinical demand for gallium-68, commercial germanium-68/gallium-68 ([68Ge]Ge/[68Ga]Ga) generators are incapable of supplying sufficient amounts of the short-lived daughter isotope. In this study, we demonstrate a high-yield, automated method for producing multi-Curie levels of [68Ga]GaCl3 from solid zinc-68 targets and subsequent labelling to produce clinical-grade [68Ga]Ga-PSMA-11 and [68Ga]Ga-DOTATATE. Results Enriched zinc-68 targets were irradiated at up to 80 µA with 13 MeV protons for 120 min; repeatedly producing up to 194 GBq (5.24 Ci) of purified gallium-68 in the form of [68Ga]GaCl3 at the end of purification (EOP) from an expected > 370 GBq (> 10 Ci) at end of bombardment. A fully automated dissolution/separation process was completed in 35 min. Isolated product was analysed according to the Ph. Eur. monograph for accelerator produced [68Ga]GaCl3 and found to comply with all specifications. In every instance, the radiochemical purity exceeded 99.9% and importantly, the radionuclidic purity was sufficient to allow for a shelf-life of up to 7 h based on this metric alone. Fully automated production of up to 72.2 GBq [68Ga]Ga-PSMA-11 was performed, providing a product with high radiochemical purity (> 98.2%) and very high apparent molar activities of up to 722 MBq/nmol. Further, manual radiolabelling of up to 3.2 GBq DOTATATE was performed in high yields (> 95%) and with apparent molar activities (9–25 MBq/nmol) sufficient for clinical use. Conclusions We have developed a high-yielding, automated method for the production of very high amounts of [68Ga]GaCl3, sufficient to supply proximal radiopharmacies. The reported method led to record-high purified gallium-68 activities (194 GBq at end of purification) and subsequent labelling of PSMA-11 and DOTATATE. The process was highly automated from irradiation through to formulation of the product, and as such comprised a high level of radiation protection. The quality control results obtained for both [68Ga]GaCl3 for radiolabelling and [68Ga]Ga-PSMA-11 are promising for clinical use.

Synthese eines Doppel-Carbodiphosphorans und seiner Vorstufen / Synthesis of a Double-Carbodiphosphorane and its Precursors

1982 ◽  
Vol 37 (6) ◽  
pp. 677-679 ◽  
Author(s):  
Hubert Schmidbaur ◽  
Thomas Costa
Keyword(s):  
Phosphonium Salt ◽  
Ring Structure ◽  
Membered Ring ◽  
Phosphonium Bromide ◽  
High Yields

Abstract The reaction of 1,4-dibromobutane with bis(diphenylphospliino)methane (1) yields two products, one of which is identified as butane-1,4-bis[diphenyl(diphenylphosphinomethyl)-phosphonium bromide] (3 a). Transylidation of this bis-phosphonium salt using two equiv-alents of (CH3)3P = CH2 affords the bis-ylide [CH2CH2P(C6H5)2 = CH-P(C6H5)2]2 (4) in high yields. This conversion can be reversed on treatment of 4 with etheral HCl (to give 3b). Methylation of 4 with CH3I occurs at phosphorus, however, and produces the bis-semiylide salt (5), [CH2CH2P(C6H5)2CHP(C6H5)2CH3]22⊕ 2I⊖. Transylidation of 5 (again with (CH3)3P = CH2) leads to the bis-carbodiphosphorane (6), [CH2CH2P(C6H5)2 = C = P(C6H5)2CH3]2. All compounds were characterized by elemental and detailed NMR analyses. The second product of the above quaternisation reaction is a cyclic bis-phosphonium salt (2) with a seven-membered ring structure.

Dipeptide-Based Phosphonium Salt Catalysis: Application to Enantioselective Synthesis of Fused Tri- and Tetrasubstituted Aziridines

Synlett ◽  
2019 ◽  
Vol 30 (19) ◽  
pp. 2101-2106 ◽  
Author(s):  
Jia-Hong Wu ◽  
Jianke Pan ◽  
Tianli Wang
Keyword(s):  
Phosphonium Salt ◽  
Phase Transfer ◽  
Asymmetric Reactions ◽  
Phosphonium Salts ◽  
Catalytic Systems ◽  
The Past ◽  
Versatile Tool ◽  
Quaternary Phosphonium Salt ◽  
Near Future ◽  
New Phase

Over the past decades, phase-transfer catalysis (PTC), generally based on numerous chiral quaternary ammonium salts, has been recognized as a powerful and versatile tool for organic synthesis in both industry and academia. In sharp contrast, PTC involving chiral phosphonium salts as the catalysts is insufficiently developed. Recently, our group realized the first enantioselective aza-Darzens reaction for preparing tri- and tetrasubstituted aziridine derivatives under bifunctional phosphonium salt catalysis. This article briefly discusses the recent development in asymmetric reactions (mainly including nucleophilic additions and cyclizations) promoted by chiral quaternary phosphonium salt catalysts. We expect that more catalytic asymmetric reactions will be developed on the basis of such new phase-transfer catalytic systems in the near future.

Reductions with sulfurated borohydrides. V. Reductions of ketones

1970 ◽  
Vol 48 (15) ◽  
pp. 2366-2371 ◽  
Author(s):  
J. M. Lalancette ◽  
A. Freche
Keyword(s):  
High Temperature ◽  
Carbonyl Group ◽  
Sodium Borohydride ◽  
Room Temperature ◽  
High Yield ◽  
High Yields ◽  
Very High

Ketones can be reduced with sulfurated sodium borohydride. Very high yield (≈90%) of the corresponding alcohol is obtained with the appropriate ratio of ketone and hydride at room temperature. The reaction is much influenced by the steric environment around the carbonyl group. At high temperature (65°) disulfides and tetrasulfides are produced. In some cases the structure of those sulfides have been established. Conjugated ketones can be reduced to the corresponding alcohols with very high yields.

scholarly journals Action of tetrabutylammonium tribromide with para-substituted chalcones in protic and aprotic media

1995 ◽  
Vol 73 (9) ◽  
pp. 1526-1530 ◽  
Author(s):  
Jacques Berthelot ◽  
Yamina Benammar ◽  
Bernard Desmazières
Keyword(s):  
Double Bond ◽  
Main Reaction ◽  
Aprotic Solvents ◽  
Mild Conditions ◽  
Tetrabutylammonium Tribromide ◽  
High Yields

Bromination of the double bond of para-substituted chalcones under mild conditions in aprotic solvents is accomplished with high yields using tetrabutylammonium tribromide (TBABr3). In methanol, the main reaction is (α-β) bromomethoxylation. Stereoselectivity, regioselectivity, and chemioselectivity of this bromomethoxylation reaction are described. Keywords: bromination, bromomethoxylation, tetrabutylammonium tribromide, (α-β) dibromodihydrochalcones, α-bromo, β-methoxydihydrochalcones.

scholarly journals New Uncharged 2-Thienostilbene Oximes as Reactivators of Organophosphate-Inhibited Cholinesterases

2021 ◽  
Vol 14 (11) ◽  
pp. 1147
Author(s):  
Milena Mlakić ◽  
Tena Čadež ◽  
Danijela Barić ◽  
Ivana Puček ◽  
Ana Ratković ◽  
...  
Keyword(s):  
Docking Studies ◽  
New Class ◽  
Nerve Signal ◽  
Central Nervous Systems ◽  
Cns Activity ◽  
High Yields ◽  
Further Development ◽  
The Brain ◽  
Very High ◽  
Inhibited Enzyme

The inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) by organophosphates (OPs) as nerve agents and pesticides compromises normal cholinergic nerve signal transduction in the peripheral and central nervous systems (CNS) leading to cholinergic crisis. The treatment comprises an antimuscarinic drug and an oxime reactivator of the inhibited enzyme. Oximes in use have quaternary nitrogens, and therefore poorly cross the brain–blood barrier. In this work, we synthesized novel uncharged thienostilbene oximes by the Wittig reaction, converted to aldehydes by Vilsmeier formylation, and transformed to the corresponding uncharged oximes in very high yields. Eight trans,anti- and trans,syn-isomers of oximes were tested as reactivators of nerve-agent-inhibited AChE and BChE. Four derivatives reactivated cyclosarin-inhibited BChE up to 70% in two hours of reactivation, and docking studies confirmed their productive interactions with the active site of cyclosarin-inhibited BChE. Based on the moderate binding affinity of both AChE and BChE for all selected oximes, and in silico evaluated ADME properties regarding lipophilicity and CNS activity, these compounds present a new class of oximes with the potential for further development of CNS-active therapeutics in OP poisoning.

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