Trimethylamine A-oxide

The isomeric pyridazino[4,5-6]azepine 19 is obtained directly during the decomplexation of the [4 + 2] adduct 17 formed from tricarbonyl(ethyl +17/-azepine-l-carboxylate)iron and 1,2,4,5-tetrazine-3,6-dicarboxylate, with trimethylamine A-oxide.113 Surprisingly, decomplexation of adduct 17 with tetrachloro-l,2-benzoquinone yields only the dihydro derivative 18 (71 %), aromatization of which is achieved in high yield with trimethylamine A-oxide in refluxing benzene. 

A convenient route to both saturated and unsaturated acylsilanes lies in the hydroboration-oxidation of alkynylsilanes (Chapter 7). Recent improvements (6) to this method involve the use of the borane-dimethyl sulphide complex for hydroboration, and of anhydrous trimethylamine A-oxide for the oxidation of the intermediate vinyl boranes. 

King GF, DJ Richardson, JB Jackson, SJ Ferguson (1987) Dimethyl sulfoxide and trimethylamine-A-oxide as bacterial electron acceptors use of nuclear magnetic resonance to assay and characterise the reductase system in Rhodobacter capsulatus. Arch Microbiol 149 47-51. 

The 1,2-diamines 41 (R = C6H13, PhCH2 or 4-MeOC6H4CH2) result from the action of trimethylamine A -oxide on the aziridine 40 in the presence of lithium iodide and Fe3(CO)i271. 

In further reactivity studies, Franck-Neumann has shown112 that a range of products such as 155 may be isolated by the trimethylamine A-oxide-promoted decomplexation of vinylketene complexes. 

Decomplexation of the vinylketene complex 185.b with trimethylamine A-oxide affords the ethyl ester 190 in 48% yield. 

All reactions are carried out under N2 atmosphere with use of standard Schlenk techniques. Solvents are dried appropriately before use. Ceo (99.5%, Southern Chemical Group, LLC) is used without further purification. Anhydrous trimethylamine A-oxide (mp 225-230°C) was obtained from Me3N0-2H20 (98%, Aldrich) by sublimation (3 times) at 90-100°C under vacuum. 

Trimethylamine-A-oxide reduc- Bacterial a2 LMo( )s,h Unknown Unknown 82,297... 

This conversion is a clean reactivity model for the Mo enzyme trimethylamine A-oxide reductase. The molybdenum(VI) bis(oxido) complex has a distorted octahedral geometry [181],... 

Reactions of trimethylamine A-oxide have been mentioned as synthetically useful and relevant to the reaction of trimethylamine A-oxide reductase [82], Sarkar and coworkers have also reported the reactions with C02, HS03 [189], and acetylenes [186]. Sarkar and Das reported [190] that WO(mnt)22 reacts with C02/HC03 to form HCOO and W02(mnt)22. This formal reduction of C02... 

Hydrophobic and osmophobic effects are important not only in the folding of individual polypeptide chains into compact globular proteins, but also in the assembly of multiprotein complexes. Osmophobic effects are noted, for instance, in the self-assembly of subunits of the glycolytic enzyme phosphofructokinase (PFK). Self-assembly is enhanced by the presence of stabilizing organic cosolvents such as trimethylamine-A-oxide (TMAO) (Hand and Somero, 1982). As discussed later, self-assembly driven by osmophobic effects results from the thermodynamic favorability of minimizing the surface area on the proteins that is in contact with the cosolvent. 

Figure 6.1. Compositions and concentrations of intracellular and extracellular fluids of selected marine animals having widely different total osmolarities. M = intracellular fluids of muscle tissue PI = plasma or hemolymph TMAO = trimethylamine-A-oxide Bet = glycine betaine FAA = free amino acids. (Data compiled from various sources for a comprehensive list of osmolyte compositions and concentrations in diverse species, see Kirschner, 1991 Somero and Yancey, 1997 Yancey et al., 1982.)...

A very specific yet interesting epoxidation method for bicyclic a,(3-unsaturated sulfones has been reported <07SL1948>. Reaction of bicyclic sulfone 10 with A-methylmorpholine N-oxide (NMO) provides the epoxide product in generally good yields. Other amine oxides such as trimethylamine A-oxide work in this reaction, however non-strained sulfones do not react even with heating. 

The parent TMM complex (190 R = H) undergoes photochemical ligand substitution with trifluorophosphine or trimethylamine Al-oxide assisted substitution with tertiary phosphines or t-butyl isocyanide (Scheme 5A) Trimethylamine A-oxide assisted substitution using isoprene as the incoming ligand results in C-C bond formation to afford the bis-TT-allyl complex (197). An intramolecular version of this reaction is also known.The parent complex (190 R = H) reacts with electrophiles. Addition of HCl or Br2 gives the methallyl complexes (192) and (198), respectively. Tetrafluoroethylene adds across the Fe bond to afford (199) under photochemical conditions. Complex (190) undergoes Friedel-Crafts-type acylation with... 

The enzymes are subdivided into three families based on structural and sequence comparisons (Figure 1, Table 1). Oxotransferases isolated from prokaryotes (see Prokaryote) belong to the DMSO reductase family. These enzymes include DMSO reductase, biotin X-oxide reductase, trimethylamine A-oxide reductase, dissimilatory nitrate reductase, formate... 

Enzymes in this family include DMSO reductase, biotin 5-oxide reductase, dissimilatory nitrate reductase, trimethylamine A-oxide reductase, and formate dehydrogenase they are found exclusively in bacteria and fungi and act as terminal respiratory reductases during anaerobic growth in the presence of their respective substrates. " DMSO reductases catalyze the reaction shown in equation (5) the water-soluble enzymes from the purple phototrophic bacteria R. capsula-tus and R. sphaeroides are among the simplest Mo-MPT enzymes, being relatively small (ca. 85 kDa), single subunit... 

AIBN = 2,2 -azobisisobutyronitrile 9-BBN = 9-borabicyclo [3.3.1]nonane Bn = benzyl BOC = f-butoxycarbonyl Bz = benzoyl CAN = ceric anunoninm nitrate Cp = cyclopenta-dienyl Cy = cyclohexyl DAST = diethylaminosnllur trifln-oride DBA = l,3-dibromo-5,5-dttnethylhydantoin DDQ = 2,3-dichloro-5,6-dicyano-l,4-benzoquinone DET = diethyl tartrate DIAD = diisopropyl acetylene dicarboxylate DIBAL-H = diisobutylalummum hydride DIPEA = diisopropyl ethyl amine DMDO = dimethyldioxirane HMPA = hexamethylphosphortriamide EDA = lithium diisopropy-lamide Ms = methylsulfonyl MOM = methoxymethyl NBS = iV-bromosuccmimide NMO = A-methylmorpholine iV-oxide PDC = pyridinium dichromate PMP = p-methoxyphenyl THP = tetrahydropyranyl TIPS = trisiso-propylsilyl TMANO = trimethylamine A-oxide TBDMS = t-butyldimethylsilyl Tf = trifluoromethanesulfonyl TMP = 2,2,6,6-tetramethylpiperidyl TMS = trimethylsilyl Ts = p-toluenesulfonyl. 

Water can be used as the solvent in the presence of added surfactants. Reactions in ionic liquids and supercritical fluids are also feasible. A variety of reagents promote cychzation, which can be achieved at room temperature. Examples of compounds that promote and accelerate the reaction include A-methyhnorphohne A-oxide, trimethylamine A-oxide, phosphine oxides, dimethylsulfoxide, alkyl methyl snlfides, molecular sieves, and lithium perchlorate. A comparison of a few promoters is seen in Scheme 246. Promoters... 

The use of thallium is covered later, but it is worthwhile mentioning here that in the hydroxylation of polystyrenes reported by BuUen et al. the mercury or thallium intermediates were converted to the boronic acid residue using diborane and the boroiutte then transformed into the phenol (30) using hydrogen peroxide or trimethylamine A/-oxide. 

For the oxidation of alkenes, osmium tetroxide is used either stoichiometrically, when the alkene is precious or only small scale operation is required, or catalytically with a range of secondary oxidants which include metal chlorates, hydrogen peroxide, f-butyl hydroperoxide and N-methylmorpholine A -oxide. The osmium tetroxide//V-methylmorpholine A -oxide combination is probably the most general and effective procedure which is currently available for the syn hydroxylation of alkenes, although tetrasubstituted alkenes may be resistant to oxidation. For hindered alkenes, use of the related oxidant trimethylamine A -oxide in the presence of pyridine appears advantageous. When r-butyl hydroperoxide is used as a cooxidant, problems of overoxidation are avoided which occasionally occur with the catalytic procedures using metal chlorates or hydrogen peroxide. Further, in the presence of tetraethylam-monium hydroxide hydroxylation of tetrasubstituted alkenes is possible, but the alkaline conditions clearly limit the application. 

---