98039-84-0Relevant academic research and scientific papers
ELECTRON DONATION CAPABILITY OF THE TRIMETHYLSILYLOXY SUBSTITUENT AS STUDIED BY PHOTOELECTRON SPECTROSCOPY AND ELECTRON SPIN RESONANCE OF POLYSUBSTITUTED BENZENE DERIVATIVES
Kaim, Wolfgang
, p. 1 - 8 (1985)
Poly-trimethylsilyloxy substituted benzenes have been studied by UV photoelectron spectroscopy (PES).The observed ionization energies show that the OSiMe3 group is a stronger donor than the methyl group but a weaker donor than OMe or CH2SiMe3 groups.Highly substituted derivatives yield radical cations on oxidatopn with AlCl3/CH2Cl2/Me3SiCl; the electron spin resonance (ESR) as well as the PE results indicate dominating nO/? interaction, with little or no ?O-Si/? hyperconjugation, for the radical cation ground state.
Convenient syntheses, spectroscopic and structural characterisation of bi-functional boranes
Aldridge,Calder,Cunningham,Malik,Steed
, p. 188 - 194 (2007/10/03)
The first examples of bi-functional borane derivatives based around a 1,2,4,5-tetrasubstituted benzene framework are reported. Synthesis of ClBO2C6H2O2BCl (4) is accomplished in three steps (69% overall yield) through the intermediacy of the trimethylsilyl derivative 1,2,4,5-(Me3SiO)4C6H2 (3). The bis(borane) species HBO2C6X2O2BH (X=H, 7; X=Cl, 8) on the other hand, can be synthesised in a single step from substituted para-quinone precursors. Crystal structures are reported for compounds 3 and 4.
Triarylmethyl radicals and the use of inert carbon free radicals in MRI
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, (2008/06/13)
A radical compound of formula Ia wherein: each Ar12, which may be the same or different, represents a 6-membered carbocyclic, at least one group Ar12 being a group Ar1 ; each group Ar1 represents a 6-membered ring optionally substituted at the or any ortho carbon by a group R1, R2, R3 or R4, at the or any meta carbon by a group R2 or R3, and at any para carbon by a group R1, R2, R3 or R4, with the proviso that no more than two ring carbons are unsubstituted; each of R1, R2, R3 or R4, which may be the same or different, independently represents a group of formula --M, --XM, --XAr2 or --Ar2 ; M represents a water solubilizing group, each group X, which may be the same or different, represents an oxygen or sulphur atom or a NH or CH2 group.
Reaction of some Dihydrobenzoxazaphosphorinones with Nucleophiles; Unusual Oxidation, Insertion, and Rearrangement Products and their Characterisation by Single-Crystal X-Ray Analysis
Neda, Ion,Fischer, Axel,Kaukorat, Thomas,Jones, Peter G.,Schmutzler, Reinhard
, p. 1579 - 1586 (2007/10/02)
The reaction of 2-chloro-1,2-dihydro-1-methyl-4H-3,1,2-oxazaphosphorin-4-one (2) and its 2-diethylamino-substituted derivative 3 with various nucleophiles yielded novel and sometimes unexpected products.Hydrolysis of 2 furnished the 2-hydroxybenzoxazaphosphorinone 4.In the presence of small amounts of water, two molecules of 4 were transformed into 5, accompanied by cleavage of one of the heterocyclic rings.The reaction of 2 with sodium chlorodifluoroacetate led, possibly in an Arbuzov-type reaction, to compound 6.The 1,5-diaza-4,8-cyclooctanedione system 7 was formed by reaction of 2 with 1,2,4,5-tetrakis(trimethylsilyloxy)benzene with concomitant loss of the phosphorus-containing group. 2,2'-Bis(trimethylsiloxy)biphenyl reacted with 2 in the expected fashion to form the diphosphorus compound 8.From 8 the chlorogold(I) complex 9 was obtained.The reaction of 3 with tetrachloro- and tetrabromo-o-benzoquinone did not lead to the expected spirocyclic products by oxidative addition of the quinone system to λ3P.Instead, cleavage and expansion of the heterocyclic ring system with formation of the tricyclic derivatives 10 and 11 took place.Compounds 5-10 were subjected to X-ray structure analysis.Compound 5 exists as two modifications 5a and 5b, which differ mainly in the relative orientation of the phenyl rings; intramolecular N - H***O hydrogen bonds are observed.Bond lengths at the halo-substituted carbon atom in 6 indicate steric crowding.The central 8-membered ring of 7 displays a "tub" conformation.Compound 8 undergoes a conformational change on complexation to the two gold(I) centres; one of the torsion angles C - O(exocyc.)-P-N is -163 deg in 8, but 95 deg in 9.The structure determination of 10 served only to confirm the (unexpected) connectivity; the crystal quality was too poor to allow quantitative conclusions. - Key Words: Benzoxazaphosphorinones / Rearrangements / Ring-expansion reaction / Insertion reaction / Gold complex
