4- N- 1- 4,4-Dimethyl

N-(Thexyl dimethylsilyl)dimethylamine (N-[2,3-dimethyl-2-butyl]dimethylsilyl dimethyl-amine) [81484-86-8] M 187.4, b 156-160°/720mm. Dissolve in hexane, filter, evaporate and distil. Colourless oil extremely sensitive to humidity. It is best to store small quatities in sealed ampoules after distillation. For estimation of purity crush an ampoule in excess O.IN HCl and titrate the excess acid with O.IM NaOH using methyl red as indicator. [Helv Chim Acta 67 2128 1984.]... 

N-[2,3-Dimethyl-butyl-(2)J-hydroxylaminium-oxalat8 5,98 g (0,04 Mol) 3-Chlor-2-nitroso-2,3-dimethyl-butan in 150 m/ abs. Diathylather werden unter Stickstoff mit einer Losung von 1,52 g (0,04 Mol) Lithiumalanat in 40 ml abs. Diathylather 4 Stdn. am RiickfluB erhitzt. Man kiihlt die Mischung ab, zersetzt mit Wasser, filtriert den Niederschlag, wiischt mit Diathylather, trocknet das Filtrat mit Natriumsulfat und gibt eine ather. Losung von wasserfreicr Oxalsaure zu. Das isolierte Oxalat wird aus Alkohol/Diathyliither umkristallisiert Ausbeute 3,6 g (5511/, d.Th.) F 156° (Zers.). 

N-(2,3-Dimethyl-phenyl)- -methylester E4, 466 (SM -> SR) N-(l-Methyl-2-phenyl-ethyl)- (Salze) E4, 461 (CS2 + Amin)... 

Sulfimid S,S-Dimethyl-N (2,3-dimethyl-phenyl)- Ell, 905 (R2SO + Amin)... 

SaUcylaIdehyd-[2.5-di]]iethyI-phenyl hj azoa] 16 1176. N-[2.3-Dimethyl-phenyl]-N -benzoyl-nydrazin 15, 563. 

C2N3 N N N — — l,3-Dimethyl-4-(l,2,3-triazolyl) sulfide 3-methyl-2-phenyl-l,2,3-triazol-l-ine-4-thione... 

Naphth[2,l-d]oxazolium iodide, 2,3-dimethyl-reactions, 6, 215 Naphthyridine, amino-reactions, 2, 598 Naphthyridine, N-amino-reactions, 2, 596 Naphthyridine, 3-bromo-reactions... 

Pyrido[2,3-b]pyrazinium salts, N-aryl-2,3-dimethyl-nucleophilic attack, 3, 253 Pyrido[2,3-(i]pyrazinium salts reactions... 

Westphal synthesis, 2, 566 Woodward synthesis, 2, 551, 552 Quinolizinium salts, l-acetylamino-2,3-dimethyl-oxidation, 2, 540 Quinolizinium salts, 1-amino-synthesis, 2, 541 Quinolizinium salts, 2-amino-applications, 2, 569 diazotization, 2, 542 N-substituted... 

The reactions with nucleophiles include a wide variety such as amines, sulfides (133,135), diazomethane (111), and others. Of particular interest were the reactions of such intermediate iminium salts with 2,3-dimethyl-butadiene to give cyclic products as shown in the reaction of N-bromo-methylpiperidine and N-bromo- and N-chloromethyldiethylamine (134). 

To a stirred solution of 2,3-dimethyl indole (6, 1.45 g, 10 mmol, 1.0 equiv) and tetra-n-butylammonium sulfate (3.40g, 10 mmol, 1.0 equiv) in chloroform (150 mL) was added potassium hydroxide (50% aqueous solution, 20 mL) over 30 minutes. The stirring was continued for six hours, at which time the mixture was extracted with chloroform, the chloroform-water mixture was washed with water, and the organic layer concentrated. Silica gel chromatography provided 2,4-dimethyl-3-chloroquinoline (7, 1.52 g, 79% yield). 

PPA and AcOH at 100°C for 4 h gave 9-hydroxy-2,3-dimethyl-4/f-pyrido-[1,2-n]pyrimidin-4-one in 24% yield (96EUP733633). Reaetion of 2-aminopyridine and ethyl 2-aeetoxyaeetoaeetate in boiling EtOH gave 2-methyl-3-hydroxy-4//-pyrido[l,2-n]pyrimidin-4-one in 47% yield (94KFZ(10)23). 

Aniline, 2-chloro- [Benzenamine 2-chloro-], p-bromination of, 55, 23 Aniline, 3 chloro- [Benzenamine, 3-chloro-], p bjomination of, 55, 23 Aniline, //.A -diethyl- [Benzenamine, N,N-diethyl-], p-bromination of, 55, 23 Aniline,TV,//-dimethyl- [Benzenamine, N,N-dimethyl-], p-brommation of, 55, 23 Aniline, 2,3-dimethyl- [Benzenamine, 2,3-dimethyl-], p-bromination of, 55, 23 Aniline, 2,5-dimethyl- [Benzenamine, 2,5-dimethyl-], p-biomination of, 55,23 Aniline, 3,5-dimethyl [Benzenamine, 3,5-dimethyl ], p bromination of, 55,23 Aniline, Ar,iV-dimethyl-3-(trifluoromethyl) [Benzenamine, At,Ar-dimethyl-3-tn-fluoromethyl-], 55,21 Aniline, 3-methoxy- [Benzenamine, 3-methoxy-], p-bromination of, 55, 23 Aniline, TV-methyl- [Benzenamine, //-methyl-], p-biomination of, 55, 23 Aniline, 2-methyl-//,JV-dimethyl- [Benzen-amme, 2/V,/V-tnmethyl-], p-bromina-tion of, 55, 23... 

Different results were obtained by Kobayashi and colleagues [76] performing the Diels-Alder reaction of 2,3-dimethyl butadiene with N-butylmaleimide in water in the presence of various dodecyl sulfate (DS) and dodecane sulfonate (DCS) LASCs [M(DS) M = Sc, Cu n = 3, 2 M(DCS) M = Sc, Yb, Mn, Co, Cu, Zn, Na, Ag n = 3,2, 1]. Unexpectedly, no acceleration was observed with respect to the reactions carried out in water only, and no catalytic effect was found also by using a bidentate dienophile which, in principle, should be able to coordinate the metal cation in the LASC system. 

Engberts [3e, 9] has extensively investigated the Diels Alder reaction in aqueous medium. Recently Engberts and colleagues reported [9c] a kinetic study of a Diels Alder reaction of N-alkyl maleimides with cyclopentadiene, 2,3-dimethyl-1,3-butadiene and 1,3-cyclohexadiene in different solvents. The reaction rates of the cycloadditions with the open-chain diene relative to w-hexane are reported in Table 6.3. The aqueous medium greatly accelerates the Diels Alder reaction and the acceleration increases as the hydrophobic character of the alkyl group of the dienophile increases. These and other kinetic data [3e, 9], along with the observation that the intramolecular Diels-Alder reaction is also accelerated in... 

Table 6.3 Relative reaction rates of Diels-Alder reactions between 2,3-dimethyl-1,3-butadiene and N-alkylmaleimides in different solvents at...

On the other hand, the observed syn preference of 59a is consistent with a study of hydroboration of 59a with diborane by Schueler and Rhodes [127], who obtained a mixture of the monoalcohols (symanti = 74 26) upon oxidative work-up. A similar magnitude of. yyn-preference was found (syn anti = 73 27) in the hydroboration with a bulkier borane, 2,3-dimethyl-2-butylborane (thexyl borane) [127]. This lack of effect of the bulk of the reagent in the hydroboration of 59a is consistent with the idea that the n face of 59a is free from steric bias [127], and that the syn preference of 59a found in dihydroxylation and epoxidation is non-sterically determined [128]. 

In the presence of the corresponding copper(II) catalyst, N-acryloyloxazo-lidinone reacted with various conjugated dienes (cyclic and acychc) with good enantioselectivities in all cases, competing with results obtained for classical catalysts in the case of flexible dienes. Thus the cycloadducts obtained from isoprene or 2,3-dimethyl-1,3-butadiene were synthesized in high yields and good enantioselectivities (92% ee in both cases). 

The regiochemistry of Al-H addition to unsymmetrically substituted alkynes can be significantly altered by the presence of a catalyst. This was first shown by Eisch and Foxton in the nickel-catalyzed hydroalumination of several disubstituted acetylenes [26, 32]. For example, the product of the uncatalyzed reaction of 1-phenyl-propyne (75) with BujAlH was exclusively ds-[3-methylstyrene (76). Quenching the intermediate organoaluminum compounds with DjO revealed a regioselectivity of 82 18. In the nickel-catalyzed reaction, cis-P-methylstyrene was also the major product (66%), but it was accompanied by 22% of n-propylbenzene (78) and 6% of (E,E)-2,3-dimethyl-l,4-diphenyl-l,3-butadiene (77). The selectivity of Al-H addition was again studied by deuterolytic workup a ratio of 76a 76b = 56 44 was found in this case. Hydroalumination of other unsymmetrical alkynes also showed a decrease in the regioselectivity in the presence of a nickel catalyst (Scheme 2-22). 

Isoprene or 2,3-dimethyl-l,3-butadiene or 1,3-cyclohexadiene (with Et2NH), 2,3-dimethyl-1,3-butadiene (with n-BuNH2 or piperidine) and 1,3-hexadiene or 2,4-hexa-diene (with PhNH2) similarly give 1 1 telomers in fair to good yields [186]. 

Several recent general papers on the properties of quinoxaline N-oxides have reported studies on the crystal structures of quinoxaline 1,4-dioxide,380 its 2,3-dimethyl derivative,380 ethyl 7-chloro-3-methyl-2-quinoxalinecarboxylate 1,4-dioxide,40 and N-(2-hydroxyethyl)-3-methyl-2-quinoxalinecarboxamide 1,4-dioxide 931 the NMR spectral data of quinoxaline 1,4-dioxide for comparison with those of related dioxides 348 the NMR data for biologically active quinoxalinecarboxamide dioxides 381 thermochemical data for several quinoxaline dioxides 183 and polaro-graphic or cyclic voltammetric data for 2,3-disubstituted quinoxaline dioxides.239 894... 

The synthesis of N-phenyl-1,3,4,6-tetrahydrothieno(3,4-c)-pyrrole-2,2-dioxide (II) was carried out by reacting aniline with 3,4-bis(bromomethyl)-2,5-dihydrothiophene-l,1-dioxide (I). The latter compound was synthesized by the bromination of the cycloaddition product, prepared from 2,3-dimethyl-l,3-butadiene and sulfur dioxide (17). 

In 1989 Jutzi et al. reported the reaction of decamethylsilicocene 50 with tri-n-butylphosphine selenide in benzene at room temperature, leading to almost quantitative formation of a 1,3,2,4-diselenadisiletane derivative 52, a head-to-tail [2+2] cycloaddition reaction product of the initially formed silaneselone 51.35 The intermediacy of silaneselone 51 was experimentally supported by the reaction in the presence of 2,3-dimethyl-1,3-butadiene resulting in the formation of the corresponding [2+4] cycloaddition reaction product 53 (Scheme 14). 

Fig. 3 Protonation states, isomerism and mesomerism of the HBI chromophore (p-hydroxybenzi-lidene-imidazolinone). The chromophore is shown in its most stable Z ( cw ) conformation, conventionally associated to a 0° value of the dihedral angle t, while the E ( trans ) conformation corresponds to t = 180°. For model compound HBDI (4 -hydroxy-benzylidene-2,3-dimethyl-imidazolinone), Ri = R2 = CH3, for chromophore in GFP, Ri, and R2 stand for the peptidic main chains toward N-terminus and C-terminus, respectively, (a) Possible protonation states of HBI (a) neutral, (b) anionic, (c) enolic, (d) cationic, and (e) zwitterionic. (b) Two resonance structures of the anionic form of HBI...

Pyranose and furanose forms of the methyl glycoside of 2,3-dimethyl-n-gaiacturonic acid methyl ester... 

---