B 3,4-dimethyl

Die Umsetzung von Phenolen mit Ninhydrin und 4-Methyl-anilin stellt im praparativen MaBstab eine nutzliche Alternative zur Kolbe-Schmitt-Carboxylierung dar. So erhalt man z. B. 3,4-Dimethyl-2-hydroxy-benzoesdure zu 78% aus 2,3-Dimethyl-phenol247b. 

Draw a structure for each alcohol. (a) 3-pentanol (b) 2-methyl-l-butanol (c) 3-ethyl-2-hexanol (d) ethanol 90. Draw a structure for each alcohol. (a) 1-hexanol (b) 3,4-dimethyl-2-heptanol (c) 3-propyl-3-octanol (d) 33-diethyl-2,2-dimethyl-l-hexanol... 

The photolysis of 4 in the presence of 2,3-dimethylbutadiene yields 3,4-dimethyl-l-silacyclobut(3)enes 47a,b as the reaction product of a formal [4 + 1] cyclo-... 

IR and Raman spectra were obtained for 3,4-dimethyl-l,2,5-thiadiazole 1,1-dioxide 23 and showed S=0 asymmetric and symmetric stretching at 1428 and 1168 cm, respectively <1997JMT119>. A high-resolution ca. 0.003 cm-1) gas-phase IR study of 1,2,5-thiadiazole 1 in the range 750-1250cm 1 gave five fundamental bands (B1 1225.2 cm-1, b-type in-plane CH bend), //4 (A p 1041.4cm-1, a-type in-plane CH bend), i/14 (B2 ... 

Crich and Rumthao reported a new synthesis of carbazomycin B using a benzeneselenol-catalyzed, stannane-mediated addition of an aryl radical to the functionalized iodocarbamate 835, followed by cyclization and dehydrogenative aromatization (622). The iodocarbamate 835 required for the key radical reaction was obtained from the nitrophenol 784 (609) (see Scheme 5.85). lodination of 784, followed by acetylation, afforded 3,4-dimethyl-6-iodo-2-methoxy-5-nitrophenyl acetate 834. Reduction of 834 with iron and ferric chloride in acetic acid, followed by reaction with methyl chloroformate, led to the iodocarbamate 835. Reaction of 835 and diphenyl diselenide in refluxing benzene with tributyltin hydride and azobisisobutyronitrile (AIBN) gave the adduct 836 in 40% yield, along with 8% of the recovered substrate and 12% of the deiodinated carbamate 837. Treatment of 836 with phenylselenenyl bromide in dichloromethane afforded the phenylselenenyltetrahydrocarbazole 838. Oxidative... 

Bei Einsatz von z. B. 3,5-Dimethyl-l-(imino-isopropylamino-methyl)-pyrazo]/ai-Brom-aceto-phenon erhalt man infolge Hydrolyse des nicht isolierten 2-(3,5-Dimethyl-pyrazolo)-l-isopro-pyl-4-phenyl-im idazols 2-Hydroxy-1 - isopropyl-4 -phenyl- imidazol (51 %)105 ... 

Je nach den Bedingungen bei der Nitramin-Umlagerung laBt sich z.B. in konz. Schwe-felsaure/Eisessig bzw. konz. Salzsaure/Eisessig ein Verhaltnis von 2,3-Dimethyl-1-nitro-zu 3,4-Dimethyl-1-nitro-benzol von 49/51 bzw. 17/83 einstellen1. 

Als Base dient hierbei ein doppelter OberschuB an Amin. Die Produkte (z.B. Bis-[l,l-diethyl-propinyl]-amitv, 48%) konnen, je nach Bedingungen, zu sterisch stark gehinderten primaren Aminen (z. B. H2/Pt02/Ethanol, 300 kPa 3-Amino-3-ethy -pentan 90%), sekundaren Aminen (z.B. H2/Raney-Ni/Ethanol, 420kPa Bis-[1, l-diethyl-propyl]-amin 72%) Oder cyclischen Aminen (z.B. Hj/Pd-C/Ethanol, Normaldruck, 0° 2,2,5,5-Tetra-ethyl-3,4-dimethyl-2,5-dihydro-pyrrol, 48% neben 2,2,5,5-Tetraethy -4-methyl-3-methylen-pyrrolidin 15%) hydriert werden. 

Die Diels-Alder-Reaktion von N-Sulfinyl-Verbindungen (N-Sulfinyl-carbamidsaure-ester, N-Sulfinyl-sulfonsaure-amide) mit 1,3-Dienen fiihrt zu 3,6-Dihydro-2H-l,2-thiazin-l-oxi-den, deren hydrolytische Spaltung N-(3-Alkenyl)-amide ergibt, z.B. ausgehend von ( , )-3,4-Dimethyl-2,4-hexadien stereo spezifisch threo-(E)-3,4-Dimethyl-2-( 4-methyl-benzolsulfonylamino)-4-hexen (85%)2 dieses Sulfonsaure-amid laBt sich zum threo-(E)-5-Amino-3,4-dimethyl-2-hexen hydrolysieren (s.S. 1194 und Bd. XI/1, S. 941). 

Problem 6.1 Write structural formulas for (a) 3-bromo-2-pentene, (b) 2,4-dimethyl-3-hexene, (c) 2,4,4-trimethyl-2-pentene, (d) 3-ethylcyclohexene. 

A similar study, which supports previous claims involving the 3,4-dimethylsilole and its corresponding isomeric intermediates, has been also carried out on the 3,4-dimethyl derivatives of 12 and 1320a,b. 

---