Tetramethyl piperidines

Fig. 3 Detail of the O- - I interaction in the binary system associating the 4-amino-2,2,6,6-tetramethyl(piperidin-l-yloxyl) radical 7 with pTFDIB... 

In addition, Robbins and Eastman were able to trap the intermediate phenyl-acetyl radicals by photolysis in the presence of the 2,2,6,6-tetramethyl-piperidine-l-oxyl free radical,... 

The u.v.-visible spectrum of the 4-hydroxy-2,2,6,6-tetramethyl-piperidine-N-oxyl-methyl-cobinamide is very similar to methyl-cobin-amide itself and as a result this technique cannot be used to rigorously identify the spin labeled derivative. The spin labeled compound does show a spectral change with pH between pH 7.0 and pH 2.0 which methyl-cobinamide does not exhibit. Despite the similarities between methyl-cobinamide and nitroxylmethylcobinamide, the circular dichroism spectrum of the two derivatives are quite different. Fig. 23 shows the marked difference in C. D. spectra of 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl, methylcobinamide, and a methylcobinamide solution containing an equimolar amount of uncoordinated nitroxide. 

The olefin metathesis of 3-hydroxy-4-vinyl-l,2,5-thiadiazole 112 and a McMurry coupling reaction (Ti3+ under reductive conditions) of the aldehyde 114 were both unsuccessful <2004TL5441>. An alternative approach via a Wittig reaction was successful. With the use of the mild heterogenous oxidant 4-acetylamino-2,2,6,6-tetramethyl-piperidine-l-oxoammonium perfluoroborate (Bobbitt s reagent), the alcohol 113 was converted into the aldehyde 114. The phosphonium salt 115 also obtained from the alcohol 113 was treated with the aldehyde 114 to give the symmetrical alkene 116 (Scheme 16) <2004TL5441>. 

Registration of ROS was carried out by electron paramagnetic resonance (EPR) technique using spin trap l-hydroxy-2,2,6,6-tetramethyl-piperidine-4-OH (2 x 10 3 M). EPR spectra in the samples were registered at room temperature in quartz cuvette with the volume of 200 pi (Burlaka et al., 1994). 

Monobasic solutes that have no carbinyl hydrogens may also show nonequivalence. 3-Methyl-2-butanone, 4-methyl-2-pentanone, 2-methylpropanal, methyl 2-methylbutyrate, 2,2,6,6-tetramethyl-piperidine, methyldiisopropylcarbinol, and methylethyl-n-butyl-carbinol in TFAE-saturated benzene all show nonequivalence of sufficient magnitude (0.01-0,03 ppm) to allow nonequivalence sense determination at 220 MHz. An especially striking example is that provided by pyrazolines 26. With only a severalfold excess of (S)-TFAE, 3(5),5(S)-enriched samples of these compounds show nonequivalence in their methyl resonances (downfield sense for the singlets and upfield sense for the triplets) sufficient for enantiomeric purity determination at 90 MHz (52). 

The system RuCl3(PPh3)3/TEMPO/O3(10 atm air)/CgH3Cl (TEMPO=2,2, 6,6 -tetramethyl-piperidine-iV-oxyl radical. Fig. 1.40) oxidised primary alcohols to aldehydes and secondary alcohols to ketones. Hammett correlation studies and primary... 

As expected, 2-halo-l,3-dithianes react with nucleophiles under Sn conditions. Suitable nucleophiles are enamines <2002TL9517, 2004T6931> and phenols <1997MOL7>. The reaction with EtOC(S)S K, followed by oxidation, provided a xanthate which generated a 1,3-dithiane 1-oxide radical upon treatment with Bu3SnH (Scheme 69) <2004T7781>. An efficient one-carbon radical precursor has also been obtained by addition of 2,2,6,6-tetramethyl-piperidine-l-oxyl (TEMPO) to 2-lithio-l,3-dithiane. The reactivity of this compound has been demonstrated <2005S1389>. 

Distortion of the chair conformation by substitution occurs in 2,2,6,6-tetramethyl-piperidin-4-one hydrochloride (45) (71AX(B)932), in which steric interaction between axial methyl groups leads to flattening of the ring. The resultant C(2)—C(6) intramolecular distance is 3.2 A, to be contrasted with 2.4 A in the non-methylated compound. A similar effect is to be found in other 2,2,6,6-tetramethyl derivatives (81AX(B)1771). In the related free radical nitroxide (46) the steric interactions are reduced by adoption of a symmetric twist chair form (74AX(B)790). 4-Chloro-5-methylamino-2,3,6-pyridinetrione monohydrate... 

Observations Poly(2,2,6,6-tetramethyl piperidine-4-vinyloxy-l-oxyl) was prepared... 

Under a protective nitrogen atmosphere, a reaction flask was charged with 2,2,6,6-tetramethyl piperidine-4-vinyloxy-l-oxyl (50.4 mmol) and 100 ml of CH2CI2 and then cooled to -78°C and treated with boron trifluoride diethyl ether complex (2 mmol). The mixture was stirred at -78°C for 20 hours and then warmed to ambient temperature. The solid was filtered, washed with methanol several times, dried in vacuum, and the product isolated in 70% yield as a red solid having an M of 89,000 Da with a polydispersity of 2.7, Tg of 132°C, and ESR spectrum of... 

These results refer to 1,2,2,6-tetramethyl piperidine which has a greater JV-Me preference than N-methylpiperidine. 

In the presence of 4-amino-2,2,6,6-tetramethyl-piperidine, a partial nucleophilic substitution of the bromine atom occured it resulted in the formation of a new polymeric stabilizer which has been treated by peracetic acid vapor. 

Patents state that the addition products from 2,2,6,6-tetramethyl-piperidin-4-ol and tetrolic acid are heat and light stabilizers for polymers.276-277... 

Reaction of compound 83 with 2,2,6,6-tetramethyl-piperidine-l-oxyl (TEMPO) on a preparative scale affords in a multistep reaction trisiloxane 120 as the major product in 80% yield, while with Ifii O- radical the 1 2 adduct 121 was isolated and, as a by-product, the trisilane 122 in 15% yield <20040M6330>. 

Optically active (—)-sparteine, a piperidine-derived alkaloid complexed with palladium chloride 33, has been used in the enantioselective oxidation of benzyl alcohol derivatives <2005JA14817>. 4-Hydroxy-TEMPO 34 serves as an efficient catalyst for the continuous production of aldehydes from alcohols and bleach in a tube reactor (TEMPO = 2,2,6,6-tetramethyl-piperidine-l-oxyl) <20050PD577>. 

Zhao Q, Ma L, Jiang S et al (2005) Identification of N-phenyl-N -(2,2,6,6-tetramethyl-piperidin-4-yl)-oxalamides as a new class of HIV-1 entry inhibitors that prevent gpl20 binding to CD4. Virology 339 213-225... 

LDA came into general use in the 1970s, and you may meet more modern variants derived from butyllithium and isopropylcyeiohexylamine (lithium isopropylcyclo-hexylamide, LICA) or 2,2.6,6-tetramethyl piperidine... 

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