Hartmut Oehme

Synthese von aryl-dialkylaminoalkylidenphosphinen - ein neuer zugang zu derivaten des zweifach-koordinierten dreibindigen phosphors

Zusammenfassung Aromatic primary phosphines react with carboxylic acid amide acetals to give aryldialkylaminoalkylidenphosphines. Intensive 1 H, 13 C and 31 p nmr studies prove the compounds to involve phosphorus in the trivalent dicoordinate state.

Generation and conversion of the transient 1,1-bis(trimethylsilyl)-2-( 2,4,6-triisopropylphenyl)-silene

Abstract Treatment of 2,4,6-triisopropylbenzaldehyde with tris(trimethylsilyl)silylmagnesium bromide (2) gives 2,4,6-triisopropylphenyl-tris(trimethylsilyl)silyl-methanol (3) in approximately 70% yield and E-3,4-bis(2,4,6-triisopropylphenyl)-1,1,2,2-tetrakis(trimethylsilyl)-1,2-disilacyclobutane (5) (15%). 5 is the [2 + 2] head-to-head cyclodimer of the transient 1,1-bis(trimethylsilyl)-2-(2,4,6-triisopropylphenyl)silene (4), formed by trimethylsilanolate elimination according to a Peterson mechanism from the magnesium alkoxide, derived from the alcohol 3. Deprotonation of 3 with McLi at low temperature in ether produces a complex mixture of products, the main constituents being the silene dimer 5 (10%) and bis(trimethylsilyl)-2,4,6-triisopropylbenzyl-trimethylsiloxysilane (10) (60%), which is formed by readdition of the eliminated lithiumtrimethylsilanolate at the SiC bond of 4. The deprotonation of 3 with McMgBr or PhMgBr (activated by LiBr) in THF at room temperature results in the formation of the polysilane (Me3Si)3SiSi(SiMe3)2CH2(2,4,6-C6H2iPr3) (13). Its generation indicates that there exists an equilibrium between the magnesium alkoxide derived from the alcohol 3 on one side, and the magnesium silanide 2 and 2,4,6-triisopropylbenzaldehyde on the other side. Possible pathways of the formation of the compounds mentioned, as well as of further by-products, are discussed. The 1,2-disilacyclobutane 5 is characterized by an X-ray crystal structure analysis.

THE REACTION OF TRIS(TRIMETHYLSILYL)SILYLLITHIUM WITH DIBENZOSUBERENONE

Tris(trimethylsilyl)silyllithium ( 1 ) reacts with dibenzosuberenone in ether to give, after carbonyl addition of the lithium silanide and lithium trimethylsilanolate elimination according to a modified Peterson mechanism, the transient silene 5 which is trapped by addition of excess 1 at the SiC double bond to afford 2-[5H-dibenzo[a,d]cyclohepten-5-yl]-1,1,1,4,4,4-hexamethyl-2,3,3-tris(trimethylsilyl)-tetrasilan e ( 7 ). When the same reaction is carried out in dimethoxyethane, no silene is generated, but after carbonyl addition of 1 at dibenzosuberenone a 1,3-Si,O-trimethylsilyl migration occurs, producing the lithium silanide 8 which undergoes an intramolecular addition at the 10,11-CC double bond of the dibenzocycloheptatriene system under formation of a bicyclic organolithium derivative which reacts with excess dibenzosuberenone to afford the alcohol 10 . Compounds 7 and 10 were fully characterized by their IR, NMR and MS data, for 10 the results of an X-ray crystal structure analysis are also given.

KONFIGURATIONS- UND KONFORMATIONSBESTIMMUNG AN 1.3-OXAPHOSPHORINANEN

Abstract The diastereomers of substituted 1,3-oxaphosphorinanes prepared by cyclocondensation of suitable 3-hydroxyalkylphosphines with aldehydes were assigned by means of the 13C- and 31P-chemical shifts, the coupling constants 1 J(P–C), 2 J(P–C–H), 2 J(P–C–C), 3 J(P–C–C–H) and the paramagnetic shift of the protons. The conformational equilibrium is mainly controlled by the substituent on position 2. In the trans-trans-isomer of 4,4,6-trimethyl-2,3-diphenyl-1,3-oxaphosphorinan we propose a participation of twist-boat-conformers. Die Diastereomere und Konformere substituierter 1.3-Oxaphosphorinane, hergestellt durch Cyclokondensation geeigneter 3-Hydroxyalkylphosphine mit Aldehyden, wurden mit Hilfe von 13C- und 31P-chemischen Verschiebungen, der Kopplungskonstanten 1 J(P–C), 2 J(P–C–H), 2 J(P–C–C), 3 J(P–C–C–H) sowie der paramagnetischen Verschiebungen der Protonen bestimmt. Die Lage der Konformerengleichgewichte hangt vorwiegend vom Substituenten in Position 2 ab. Im trans-trans-Isomeren des 4.4.6-Trime...

Zur bildung von 3-element-1-phosphor-heterocyclen

Abstract The reaction of sec-amino-, hydroxy- and mercapto-alkylphosphines with carbonyl compounds leads to 3-aza-, 3-oxa- and 3-thia-phospholanes or -phosphorinanes, respectively, but the interaction of diphosphines of the type RPH(CH 2 ) n PHR ( n = 2, 3) only gives α-hydroxyalkylphosphines, which are partly rearranged into t-phosphine oxides. The mechanism of the formation of 3-element-1-phosphorus heterocycles is discussed.

Geminal di(hypersilyl) compounds. The synthesis and structure of dimethylamino-bis[tris(trimethylsilyl)silyl]methane

Abstract Dimethylamino-bis[tris(trimethylsilyl)silyl]methane (5) is prepared by the reaction of tris(trimethylsilyl)silyllithium (1) with chloromethylene-dimethyliminium chloride. The proposed mechanism of the formation of 5, leading to the fixation of two bulky hypersilyl groups at one comparatively small carbon atom, is discussed. The structure of 5, elucidated by an X-ray crystal structure analysis, is characterized by tremendous distortions of the molecular skeleton due to the spatial demand of the two extended hemispherical (Me3Si)3Si groups, causing for example a central Si–C–Si angle of 132.6°.

1,3,5-Azoxaphosphorinane

Abstract 1,3,5-Azoxaphosphorinanes are formed by interaction of phenylphosphine with Schiffs bases and benzaldehyde. The structures of these new heterocyclic compounds are suggested based on their infrared and nuclear magnetic resonance spectra.

Preparation and Synthetic Utility of 1-Trimethylsiloxyalkyl-bis(trimethylsilyl)silanes, (Me3Si)2SiH-C(OSiMe3)R1R2

1-Trimethylsiloxyalkyl-bis(trimethylsilyl)silanes (5), obtained by a base induced isomerization of easily accessable 1-hydroxyalkyl-tris(trimethylsilyl)silanes (1) were hydrolized to give 1-hydroxyalkyl-bis(trimethylsilyl)silanes (6), which in presence of sodium hydride underwent a further 1,3-Si,O-trimethylsilyl migration resulting in the formation of 1-trimethylsiloxyalkyl-disilanes Me3SiSiH2–C(OSiMe3)R1R2 (7). Under acidic conditions, the alkoxysilanes 5 isomerized in a Me3Si/OSiMe3 exchange under formation of the 1-trimethylsilylalkyldisiloxanes 10, which were hydrolyzed affording the silanols 11. Chlorination of the H-silanes 5 with CCl4 gave the chlorosilanes 12, which underwent rapid thermal isomerizations to give via the 1-chloroalkyldisiloxanes 13 the 1-trimethylsilylalkyl-chlorodisiloxanes 15. Hydrolysis of 12 or 15, resp., finally afforded the 1-trimethylsilylalkyl-silanediols 18. Possible mechanisms of the various isomerization processes are discussed. The structures of the products described were elucidated by full spectral analyses. For 18 a the results of an X-ray structural analysis are given. Darstellung und synthesechemische Nutzung von 1-Trimethylsiloxyalkyl-bis(trimethylsilyl)silanen, (Me3Si)2SiH–C(OSiMe3)R1R2 1-Trimethylsiloxyalkyl-bis(trimethylsilyl)silane (5), hergestellt durch baseinduzierte Umlagerung der leicht zuganglichen 1-Hydroxyalkyl-tris(trimethylsilyl)silane (1), wurden zu 1-Hydroxyalkyl-bis(trimethylsilyl)silanen (6) hydrolysiert und in Gegenwart von Natriumhydrid einer weiteren 1,3-Si/O-Trimethylsilylwanderung zu 1-Trimethylsiloxyalkyl-disilanen Me3SiSiH2–C(OSiMe3)R1R2 (7) unterworfen. In saurem Milieu isomerisierten die Alkoxysilane 5 unter Me3Si/OSiMe3-Austausch zu den 1-Trimethylsilylalkyl-disiloxanen 10, die zu den Silanolen 11 hydrolysiert werden konnten. Die Chlorierung der H-Silane 5 mit CCl4 lieferte die Chlorsilane 12, die rascher thermischer Isomerisierung unterlagen und uber die 1-Chloroalkyldisiloxane 13 zu den 1-Trimethylsilylalkyl-chlorodisiloxanen 15 fuhrten. Hydrolyse von 12 oder 15 ergab schlieslich die stabilen 1-Trimethylsilylalkyl-silandiole 18. Mogliche Mechanismen der verschiedenen Isomerisierungsschritte werden diskutiert. Die Strukturen der beschriebenen Produkte wurden durch vollstandige spektroskopische Charakterisierung gesichert. Die Ergebnisse einer Rontgenstrukturanalyse fur 18 a werden vorgestellt.

1,2-Di(hypersilyl)-ethylene — The unexpected result of the reaction of tris(trimethylsilyl) silyllithium with formic acid methyl ester

Tris(trimethylsilyl)silyllithium reacts with methyl formate in a molar ratio of 2:1 under formation of 1,2-bis[tris(trimethylsilyl)silyl]ethene (9). As reaction intermediates formyl-tris(trimethylsilyl)silane (5) and lithium bis[tris(trimethylsilyl)silyl]methoxide (6) were identified. 6 is quenched with water to give bis[tris(trimethylsilyl)silyl]methanol (7).

Synthese und Dimerisierungsverhalten des 1,1-Bis(trimethylsilyl)-2-(2,5-diisopropylphenyl)silens/ Synthesis and Dimerization Behavior of 1,1 -Bis(trimethylsilyl)-2-(2,5-diisopropylphenyl)silene

Abstract Tris(trimethylsilyl)silylmagnesium bromide, (Me3Si)3SiMgBr, reacts with 2.5-diisopropylbenzaldehyde to give 2,5-diisopropylphenyl-tris(trimethylsilyl)silylmethanol (1). With sodium hydride in THF compound 1 undergoes a rearrangement through 1,3-Si,O-trimethylsilyl migration affording bis(trimethylsilyl)silyl-(2,5-diisopropylphenyl)-trimethylsiloxy-methane (4). The deprotonation of 1 with organolithium reagents in ether leads to the elimination of lithium trimethylsilanolate according to a modified Peterson mechanism resulting in the formation of the transient silene (Me3Si)2Si=CH(2,5-iPr2C6H3) (2). Treatment of 1 with an excess of phenyllithium in diethylether at low temperature gives 1,1,1,3,3,3-hexamethyl-2- phenyl-2-(2,5-diisopropylbenzyl)-trisilane (3), formed in a nucleophilic addition of the excess PhLi to the silene intermediate and in the hydrolytic workup. Stochiometric quantities of MeLi in diethylether at -78 °C convert compound 1 into a head-to-head dimer of the silene 1,2,3,8a-tetrahydro-5,8-diisopropyl-1 -(2,5-diisopropylphenyl)-2,2,3,3-tetrakis-(trimethylsilyl)- 2,3-disilanaphthalene (5). Compound 5, presumably the kinetically preferred product of the cyclodimerization of 2, gradually transforms into the thermodynamically stable 3,4-bis(2,5- diisopropylphenyl)-1, 1,2,2-tetrakis(trimethyl-silyl)-1,2-disilacyclobutane (6). The E/Z-isomers of 6 have been characterized by X-ray crystal structural analyses.