Beiträge zur Chemie der Si-N-Bindung XV [1]. α,ω-Dimethylchlorsilyl-substituierte Cyclodisilazane

α,ω-Dimethylchlorosily-substituted monomeric and oligomeric cyclodisilazanes were prepared by the reaction of dimethyl-dichlorosilane with hexamethylcyclotrisilazane in the molar ratios 1:1 to 1:3. The mechanism of these reactions was investigated.     

Eine cyclische Methylendiphosphinsäure: 1,3‐Dihydroxy‐1,3‐dioxo‐1,2,3,4‐tetrahydro‐1λ5,3λ5‐[1,3]diphosphinin

A Cyclic Methylenediphosphinic Acid: 1,3‐Dihydroxy‐1,3‐dioxo‐1,2,3,4‐tetrahydro‐1λ⁵,3λ⁵‐[1,3]diphosphinine Strong acids protonate 1,3‐bis(dimethylamino)‐1λ⁵,3λ⁵‐[1,3]diphosphinine ( 5 ) to give the corresponding cation. The protonation is followed by hydrolytic cleavage of the dimethylamino groups resulting in the formation of the cyclic methylenediphosphinic acid ( 6 ).     

2,2-Difluor-1,2,3-trimethyl-1,3-diaza-2λ5-phospholidin

2,2-Difluoro-1,2,3-trimethyl-1,3-diaza-2λ⁵-phospholidine The title compound 1 is obtained in about 50% yield by oxidative fluorination of 1,2,3-trimethyl-1,3-diaza-2λ³-phospholidine, 6 , with IF₅. 1 is characterized by its nmr, mass, and ir spectra.     

1,4-Dihydro-1λ5,4λ5-[1,4]diphosphinine und ein 1,4-Dihydro-1λ3,4λ3-[1,4]diphosphinin

1,4-Dihydro-1λ⁵,4λ⁵-[1,4]diphosphinines and a 1,4-Dihydro-1λ³,4λ³-[1,4]diphosphinine Reaction of thio- or dithiocarbonic acids with ethinyl amino phosphanes leads to 1,4-dihydro-1λ⁵,4λ⁵-[1,4]diphosphinine-1,4-disulfides. By this route compounds 4, 7 , and 8 have been prepared. Desulfurization of 4 with tri-n-butylphosphane results in 1,2,4,5-tetraphenyl-1,4-dihydro-1λ³,4λ³-[1,4]-diphosphinine 5 , which can be oxidized with tert-butyl-peroxide to the corresponding dioxide, 6 . From the reaction mixture of phenyl-phenylethinyl diethylamino phosphane and thioacetamide compound 4 and the unsymmetrical 1,4-dihydro-1λ⁵,4λ⁵-[1,4]diphosphinine 9 were isolated. Properties, nmr, ir and mass spectra of all new products are reported. A mechanism for the formation of 9 is suggested. The results of the X-ray structure determination of 8 and 9 are described.     

3-(Dimethylamino)-2,2-dimethyl-2H-azirin als α-Aminoisobuttersäure(Aib)-Äquivalent: Cyclische Depsipeptide durch direkte Amid-Cyclisierung

3-(Dimethylamino)-2,2-dimethyl-2H,-azirine as an α-Aminoisobutyric-Acid (Aib) Equivalent: Cyclic Depsipeptides via Direct Amid Cyclization In MeCN at room temperature, 3-(dimethylamino)-2,2-dimethyl-2H-azirine ( 1 ) and α-hydroxycarboxylic acids react to give diamides of type 8 (Scheme 3). Selective cleavage of the terminal N,N-dimethylcarboxamide group in MeCN/H₂O leads to the corresponding carboxylic acids 13 (Scheme 4). In toluene/Ph SH , phenyl thioesters of type 11 are formed (see also Scheme 5). Starting with diamides 8 , the formation of morpholin-2,5- diones 10 has been achieved either by direct amide cyclization via intermediate 1,3-oxazol-5(4H)-ones 9 or via base-catalyzed cyclization of the phenyl thioesters 11 (Scheme 3). Reaction of carboxylic acids with 1 , followed by selective amide hydrolysis, has been used for the construction of peptides from α-hydroxy carboxylic acids and repetitive α-aminoisobutyric-acid (Aib) units (Scheme 4). Cyclization of 14a, 17a , and 20a with HCI in toluene at 100° gave the 9-, 12-, and 15-membered cyclic depsipeptides 15, 18 , and 21 , respectively.     

Beiträge zur Chemie der Halogensilan-Addukte. VII [1]. 2,2′-Bipyridin-N-Oxid-Komplexe von Halogensilanen

Contributions to the Chemistry of Halogenosilane Adducts. VII. 2,2′-Bipyridine-mono-N-oxide Complexes of Halogenosilanes The new adducts SiF₄ · bipyO, SiCl₄ · bipyO, SiCl₄ · 2 bipyO, SiBr₄ · 2 bipyO, SiI₄ · 2 bipyO and SiI₄ · 3 bipyO have been prepared by the reaction of SiF₄, SiCl₄, SiBr₄ and SiI₄ with bipyO in the appropriate molar ratio. The 1:1 reaction of Si₂Cl₆ and bipyO yields the adduct Cl₃SiOSiCl₃ · bipy (reduction of the amineoxide), in a 1:2 molar ratio Cl₃SiOSiCl₃ · bipy and Cl₃SiOSiCl₃ · 2 bipyO are obtained. The latter compound is formed in the reaction of Cl₃SiOSiCl₃ · bipy and bipyO and also in the reaction of Cl₃SiOSiCl₃ and bipyO. The results show that bipyO is a stronger base than bipy with reference to the silanes investigated. Some properties of the compounds and structural investigations are reported. bipyO is chelating and silicon is hexacoordinated in all adducts. The following structures are suggested: SiX₄ · bipyO (molecular), [SiX₂ · 2 bipyO]X₂ (ionic), [Si · 3 bipyO]I₄ (ionic). In Cl₃SiOSiCl₃ · 2 bipyO both ligands are coordinated to one Si atom.     

Neue 1λ5, 3λ5-[1,3]Diphosphinine mit Thio- und Selenophosphonsäureresten – Darstellung,Kristallstruktur, NMR-Daten und Komplexbildung mit PdII

Diphosphabenzenes. VI. New 1λ⁵, 3λ⁵-[1,3]Diphosphinines with Thio and Seleno Phosphonic Acid Groups – Preparation, Crystal Structure, NMR Data, and Coordination to Pd^II Preparation of N,N,N′,N′-tetraethyl-P-phenylethinyl phosphonothioacid diamide ( 2 ) and the corresponding phosphonoselenoacid diamide ( 3 ) are described. 2 and 3 react with 1,1,3,3-tetrakis(dimethylamino)-1λ⁵,3λ⁵-diphosphete ( 1 ) to yield 1λ⁵,3λ⁵-[1,3]diphosphinine derivatives 4 and 5 . With (bzl)₂Cl₂Pd 5 forms the coordination compound 6 . All new compounds 2–6 are characterized by their nmr and ir spectra, the structures of 4–6 are further elucidated by X-ray structural analyses.