Trimeric dimethyl

CH3)2A H>1(CH3)3 (CH3)2 Tri-p-hydrido-hexamethyl-tri-aluminium = trimeres Dimethyl-aluminiumhydrid trimeres p-H-Dimethyl-alan... 

Fig. 12. Structure of trimeric dimethyl(dioxo)(pyridme)osmium(VI), 0s306(py)3(Me)6. From Ref. U81).

Introduction of Nitrogen into a Terpenoid Skeleton. The acetate-derived fragments (35) mevalonic acid (30), which yields isopentenyl pyrophosphate (31) and its isomer, 3,3-dimethyl ally pyrophosphate (32) a dimeric C -fragment, geranyl pyrophosphate (33), which gives rise to the iridoid loganin (34) and the trimer famesyl pyrophosphate (35), which is also considered the precursor to C q steroids, have already been mentioned (see Table 3... 

The ratio of cycHc to linear oligomers, as well as the chain length of the linear sdoxanes, is controlled by the conditions of hydrolysis, such as the ratio of chlorosilane to water, temperature, contact time, and solvents (60,61). Commercially, hydrolysis of dim ethyl dichi oro sil a n e is performed by either batch or a continuous process (62). In the typical industrial operation, the dimethyl dichi orosilane is mixed with 22% a2eotropic aqueous hydrochloric acid in a continuous reactor. The mixture of hydrolysate and 32% concentrated acid is separated in a decanter. After separation, the anhydrous hydrogen chloride is converted to methyl chloride, which is then reused in the direct process. The hydrolysate is washed for removal of residual acid, neutralized, dried, and filtered (63). The typical yield of cycHc oligomers is between 35 and 50%. The mixture of cycHc oligomers consists mainly of tetramer and pentamer. Only a small amount of cycHc trimer is formed. 

Allene can be converted to a trimer (compound A) of molecular formula C9H12. Compound A reacts with dimethyl acetylenedicarboxylate to give compound B. Deduce the structure of compound A. 

The dimer of 1-methyl- -pyrroline (39) was obtained by reduction of N-methylpyrrole with zinc and hydrochloric acid (132) and, together with the trimer, by mercuric acetate dehydrogenation of N-methylpyrrolidine (131). J -Pyrroline-N-oxides form dimers in a similar manner (302). Treatment of 1,2-dimethyl-zl -piperideine with formaldehyde, producing l-methyl-3-acetylpiperidine (603), serves as an example of a mixed aldol reaction (Scheme 18). 

Examples of dynamic processes involving two, three, or four identical tautomers (degenerate or autotrope annular tautomerism) have been found in pyrazoles (type 2 of Table VII). Thus, 3,5-diphenyl-4-bromopyr-azole and 3,5-di-ferf-butylpyrazole (dimers), 3,5-dimethyl-pyrazole (trimer). 

This structure rationalizes (a) the formation of mono- and, under more vigorous conditions, tetra-acetyl derivatives, (b) the methyla-tion to a dimethyl derivative still containing two active hydrogens, (c) the pyrolysis back to monomeric indole, (d) the formation of a benzylidene derivative containing the Ph CH=N— Ar ehromophore, (e) the failure to form a simple nitroso derivative, (f) the Zn/AcOH reduction of the dimethyl trimer to base C18H20N2, shown to be identical with the dihydro derivative of (26). 

A Diels-Alder type [4+2] cycloadditions of 4,5-dihydropyridazine, prepared in situ from its trimer, with 2-methyl- and 2,3-dimethyl-1,3-butadienes (65, R = H, Me R = Me) afforded a complex reaction mixture, from which 6-methyl- and 6,7-dimethyl-3,4,4n,5-tetrahydro-8//-pyrido[l,2-ftjpyridazines (66, R = H, Me R =Me) could be isolated (97CEJ1588). With 1,3-butadiene (65, R = R =H) only a mixture of endo and exo isomers 67 and 68 (R = R =H) was obtained. 

Interessante Trimere liefert 2-Mcthyl-propanal. Bei der Beschickung der beiden Elek-trodenraume einer geteilten Zelle (Platin-Elektroden) mit 2-Methyl-propanal/Tetra-butylammonium-hexafluorophosphat entsteht an der Anode 2,4,6-Triisopropyl-1,3,5-trioxan (95% d. Th.) und an der Kathode 4-Hydroxy-5,5-dimethyl-2,6-diisopropyl-l,3-dioxan (90% d. Th.), jeweils in sehr hoher Ausbeute1 ... 

Detailed information on the copolymerization of cyclic trifluoropropylmethyl-siloxane trimer and octamethylcyclotetrasiloxane is also very limited in the open literature26 27 . Recently, preparation of various amine terminated (dimethyl-tri-fluoropropyl,methyl)siloxane oligomers with varying molecular weights and backbone compositions has been reported 69115 ll7). Table 11 shows various properties of the oligomers produced as a function of composition. These types of modification play very important roles in determining the solubility characteristics and hence the compatibility of resultant polysiloxanes with other conventional organic monomers... 

Controlled synthesis and detailed characterization of triblock copolymers of di-phenylsiloxane and dimethylsiloxane has been reported by Meier and co-workers147 148), who used lithium based initiators and the cyclic trimers of dimethyl and diphenyl-... 

The reaction of [AuCl(THT)] with 2-(4,5,-dihydro-4,4,-dimethyl-2,-oxazolinyl)-thien- -yllthium (n = 3,5) affords dimeric (586) or trimeric (587) gold(I) derivatives with mixed /V,C-donor ligands.2263 Other complexes with mixed N,C donor ligands which have been prepared in a similar manner are [Au2 Fc(CFl2NMe2 2], 7 [Au2 C6Fl4(CFl2NMe2) 2],3132... 

Enzymatic enantioselective oligomerization of a symmetrical hydroxy diester, dimethyl /Lhydroxyglutarate, produced a chiral oligomer (dimer or trimer) with 30-37% ee [24]. PPL catalyzed the enantioselective polymerization of e-substituted-e-hydroxy esters to produce optically active oligomers (DP < 6) [25]. The enantioselectivity increased with increasing bulkiness of the monomer substituent. Optically active polyesters with molecular weight of more than 1000 were obtained by the copolymerization of the racemic oxyacid esters with methyl 6-hydroxyhexanoate. 

Also, the trimerization reaction was observed by using jr-allyl complexes of palladium stabilized by chelating ligands, such as 28 and 29 (38). The reaction was carried out at 70°C in dimethylformamide (DMF) or dimethyl sulfoxide (DMSO), and 1,3,6,10-dodecatetraene (27) was obtained in 60% yield at 30% conversion. 

The products of electrochemical oxidation of conjugated dienes are considerably affected by the reaction conditions such as the material of the electrode, the supporting electrolyte and the solvent. The oxidation of butadiene with a graphite or carbon-cloth anode in 0.5 M methanolic solution of NaClCU mainly yields dimerized products along with small amounts of monomeric and trimeric compounds (equation 5)1. The use of platinum or glassy carbon mainly gives monomeric products. Other dienes such as isoprene, 1,3-cyclohexadiene, 2,4-hexadiene, 1,3-pentadiene and 2,3-dimethyl-l,3-butadiene yield complex mixtures of isomers of monomeric, dimeric and trimeric compounds, in which the dimeric products are the main products. 

The synthesis of commercial nonylphenols generally proceeds through an alkylation reaction of phenols with propylene trimer [124], which itself has a spread of isomers [47]. The alkylation occurs preferentially at the para position of the phenol, but 3-6% of ortho-nonylphenol can be found in commercial products [125]. Also meta and disubstituted species have been mentioned [47]. A common feature of the isomers appears to be a dimethyl substitution of the a-carbon atom [83]. 

In high polarity solvents, such as acetonitrile, dimethyl sulfoxide, methyl acetate, and methanol, the branched dimer, 4-methyl azelate precursor, is formed in high yield. In methanol, a methoxy dimer (CH302CCgH] 4(0013)0020113) is also formed in moderate yield. Heavies contain both an acyclic methyl, 4-pentadienoate trimeric product and high molecular weight methyl, 4-pentadienoate homopolymer. Polymerization in the absence of air(48) appears to be catalyzed by traces of the tertiary phosphine which is used to prepare the palladium dimerization catalyst. 

Limited theoretical studies (31, 89) on the electron-deficient beryllium derivatives have been interpreted to imply that extensive Be—Be bonding occurs. If such bonding does occur, the increased bond length observed in the phenylethynyl(methyl)beryllium trimethylamine adduct takes on additional significance since the Be—Be distance in this derivative is increased by almost 0.3 A over that observed in dimethyl-and diethylberyllium. Moreover, if cyclic trimers are formed, then increased metal-metal distances would be likely, thus reducing the probability of stabilization of the bridged system by Be—Be bonding. Additional studies will be required both on structures and of spectroscopic properties of the species to answer these questions. 

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