2-Methylpiperidine, addition

The solution of 4-chloro-1-methylpiperidine in tetrahydrofuran was dried over calcium hydride at ice-bath temperature prior to use. When the addition of the halide was complete the reaction mixture was refluxed with stirring for one hour. In some subsequent experiments this period of refluxing was omitted with no deleterious result. 

The hindered secondary amines can be highly effective photostabilizers for various polymers (]+.,5.,.6) Various hindered amines have been shown to retard oxidation, but most share the common feature of being secondary or tertiary amines with the a-carbons fully substituted. The most widely exploited representatives of this class are based on 2,2,6,6-tetramethylpiperidine either in the form of relatively simple low molecular weight compounds, or more recently as backbone or pendant groups on quite high molecular weight additives ( i.,5.,6). The more successful commercial hindered amines contain two or more piperidine groups per molecule. Photo-protection by tetra-methylpiperidines (near UV transparent) must result from the interruption of one or more of the reactions 1 to 3. Relatively recent results from our own laboratories, and in the open literature will be outlined in this context. 

Complex formation constants could also be determined directly from UV spectrophotometric measurements. Addition of tert.-butyl hydroperoxide to a solution of nitroxide I in heptane at RT causes a shift of the characteristic absorption band of NO at 460 nm to lower wavelengths (Fig. 9). This displacement allows calculation of a complex equilibrium constant of 5 1 1/Mol. Addition of amine II to the same solution causes reverse shift of theC NO" absorption band. From this one can estimate a complex formation constant for amine II and +00H of 12 5 1/Mol (23 2 1/Mol was obtained for tert.-butyl hydroperoxide and 2,2,6,6-tetramethylpipe-ridine in ref. 64b). Further confirmation for an interaction between hindered amines and hydroperoxides is supplied by NMR measurements. Figure 10a shows part of the +00H spectrum in toluene-dg (concentration 0.2 Mol/1) with the signal for the hydroperoxy proton at 6.7 ppm. Addition of as little as 0.002 Mol/1 of tetra-methylpiperidine to the same solution results in a displacement and marked broadening of the band (Fig. 10b). 

Asymmetric Michael addition of nitromethane to a crotonyl camphorsultam gives access to the enantio-pure 2-oxoesters, which may be converted into the 3-hydroxy-5-methylpiperidin-... 

Venoms from the fire ants Solenopsis invicta and 5. geminata are free of detectable histamine but possess histamine-release activity. This activity can account for the edema, itch, redness, warmth, and possibly the pain and burning sensations resulting from fire ant stings. And it can be attributed to the piperidines which constitute the major component of the venom. It has actually been proved that 6-methyl-2-n-undecylpiperidines (Ic and Id), components of S. geminata, possess the histamine-release activity (75). Due to some of the above-mentioned various activities the piperidine alkaloids play roles as defensive compounds. In addition to 2-alkyl-6-methylpiperidines, their N-methyl derivatives (3) are found in S. pergandei, S. carolinensis, and S. conjurata, and 1-piperideine derivatives (6 and 7) in S. sp. A (Puerto Rico) and S. xyloni (Table I). 

Furthermore, thianthrene react with 2-diazo(fluoroalkyl)acetoacetates under mild conditions in the presence of catalytic Rh2(OAc)4 to afford the corresponding sulfonium ylides as the major products <2004JFC(125)1071>. In addition to all the desulfurization conditions reported in CHEC-II(1996) <1996CHEC-II(6)447>, a new efficient reagent was developed. Introduction of the sodium salt of 3-hydroxy-A-methylpiperidine into the aggregates of NiCRA s (NaH-RONa-NiX2) led to 83% yield of desulfurized thianthrene in 30 min <1998TL8987>. 

Addition of piperidine to acetylenic esters is, surprisingly, asserted to be independent of both solvent and base.269 iV-Methylpiperidine adds to MP in highly aqueous media giving the betaine 64.270 Winterfeldt and Krohn271 added TV-hydroxypiperidine to DMAD and obtained the single adduct 65. 

The need to better control surface-initiated polymerization recently led to the development of controlled radical polymerization techniques. The trick is to keep the concentration of free radicals low in order to decrease the number of side reactions. This is achieved by introducing a dormant species in equilibrium with the active free radical. Important reactions are the living radical polymerization with 2,2,4,4-methylpiperidine N-oxide (TEMPO) [439], reversible addition fragment chain transfer (RAFT) which utilizes so-called iniferters (a word formed from initiator, chain transfer and terminator) [440], and atom transfer radical polymerization (ATRP) [441-443]. The latter forms radicals by added metal complexes as copper halogenides which exhibit reversible reduction-oxidation processes. 

Later it was described the synthesis of the donepezil HCI from 5,6-dimethoxy-2-(pyridin-4-yl)methylene-indan-l-one by the reaction with H2 over platinum dioxide at room temperature in acetic acid-methanol mixture to give 4-[(5,6-dimethoxy-l-indanon)-2-yl]methylpiperidine. The last one yielded donepesyl HCI by refluxing with benzyl bromide and triethylamine for 4 hours with the following addition of methanolic HCI (10%). 

A mixture of 96.5 g 2-methylsulfonylphenothiazine, 50 g 2-(2-chloroethyl)-l-methylpiperidine, 62 g diethyl carbonate and 2 g sodium methylate was heated at 135°C for 1 hour and then at 180-190°C for 2.5 hours. The product was dissolved in benzene (500 ml) and the solution was extracted with 700 ml of 15% aqueous solution tartaric acid. The extract was washed with benzene. After addition of sodium carbonate solution to the extract was obtained a precipitate which was dissolved in benzene. This solution was washed with water and concentrated. 2-Methylsulfonyl-10-(2-(l-methyl-2-piperidyl)ethyl)phenothiazin was recrystallized from acetone, melting point 121-123°C. 

Alkyl-6-methylpiperidines have only been detected in the venoms of Solenopsis workers and their queens (16, 17, 18). These compounds, which are sometimes referred to as solenopsins, are consistent poison gland products of Solenopsis species in the subgenus Solenopsis, the fire ants ( T7, 3J3J. In addition, some species in the subgenus Diplorhoptrum (thief... 

A7-methylpiperidines in 5% acetic acid produces much l,l -dimethyl-A 2-tetrahydroanabasine (3,2 -bound dimeric piperidine) in addition to 1,2,3,4-tetrahydropiperidines.189... 

Reactivity Toward Oxygen, Hydrogen Donors, and Additives This is exemplified by the following results obtained for the reaction between initiating radicals and propagating radicals and well-known radical polymerization inhibitors such as oxygen, HQME (hydroquinone methylether) or TEMPO (2,2,6,6, tetra-methylpiperidine N-oxyl radical). 

A first attempt towards an asymmetric synthesis by the lithiation reaction used (— )-spartein as a chiral additive [12,13], but the enantioselectivity was disappointing. With the chiral (S)-M-ferrocenylmethyl-2-methylpiperidine, a high diastereoselec-tivity was observed [12, 13, 112] (note that the polemic about the structure of the product is due to different stereochemical nomenclature, i.e., central vs. planar , as discussed in Sect. 4.1). A breakthrough was achieved by the readily resolvable... 

Boa-L-Leuoine N-msthyl-O-methyloarboxamide. A 1-L, three-necked, round-bottomed flask is equipped with a mechanical stirrer, an electronic digital thermometer, and a graduated addition funnel. The flask is charged with 39.1 g (0.4 mol) of N,0-dimethylhydroxylamine hydrochloride (Note 1) and 236 mL of methylene chloride (Note 2). The suspension is stirred and cooled to 2°C with an ice-water bath. N-Methylpiperidine (Note 3), 48.8 ni. (0.41 mol), is placed in the addition funnel and added dropwise while the temperature is maintained at 2° + 2°C. A clear, colorless solution results which is kept cold and used in the following reaction. 

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