3.4- Dichloro 1 ,2,3,4-tetramethyl

The reaction of l,3-dichloro(tetramethyl)siloxane 12 with f-butyl hydroperoxide in the presence of pyridine in ether gave l-f-butylperoxy-3-chlorotetramethyldisiloxane 13 in 60% yield (equation 19). 

Chroman-2-ylmethanol, (5)-6-hydroxy-2,5,7,8-tetramethyl-synthesis, 3, 779 Chromene, 3-acetyl-2-methoxy-synthesis, 3, 750 Chromene, 2-alkyl-synthesis, 3, 749 Chromene, 4-aryloxymethyl-synthesis, 3, 742-743 Chromene, bis(2,2-dimethyl-mass spectra, 3, 604 Chromene, 2,3-dichloro-synthesis, 3, 753 Chromene, 2,2-dimethyl-IR spectra, 3, 594 mass Spectra, 3, 604 molecular dimensions, 3, 621 synthesis, 3, 743, 749, 751 Chromene, 3-fluoro-2,2-dimethyl-synthesis, 3, 748 Chromene, 5-hydroxy-synthesis, 3, 745... 

The present method of preparation of 4,4 -dimethyl-l,l -biphenyl is that described by McKillop, Elsom, and Taylor 15 It has the particular advantages of high yield and manipulative simplicity and is, moreover, applicable to the synthesis of a variety of symmetrically substituted biaryls 3,3 - and 4,4 -Disubstituted and 3,3, 4,4 -tetrasubstituted 1,1 -biphenyls are readily piepared, but the reaction fails when applied to the synthesis of 2,2 -disubstituted-l,T biphenyls The submitters have effected the following conversions by the above procedure (starting aromatic bromide, product biphenyl, % yield) bromobenzene, biphenyl, 85,1 -bromo-4-methoxybenzene, 4,4 -dimethoxy-l, 1 -biphenyl, 99, 1 bromo 3 methylbenzene, 3,3 dimethyl-1,l -biphenyl, 85 4-bromo-l,2-dimethylbenzene, 3,3, 4,4 -tetramethyl-l,l -biphenyl, 76, l-bromo-4-chlorobenzene, 4,4 -dichloro-l,l -biphenyl, 73, l-bromo-4-fluorobenzene, 4,4 -difluoro-l,l -biphenyl, 73... 

Synthesis of isomeric chiral protected (63 )-6-amino-hexahydro-2,7-dioxopyrazolo[l,2- ]pyrazole-l-carboxylic acid 280 is shown in Scheme 36. Crude vinyl phosphonate 275, obtained by treatment of diethyl allyloxycarbonylmethyl-phosphonate with acetic anhydride and tetramethyl diaminomethane as a formaldehyde equivalent, was used in the Michael addition to chiral 4-(f-butoxycarbonylamino)pyrazolidin-3-one 272. The Michael addition is run in dichloro-methane followed by addition of f-butyl oxalyl chloride and 2 equiv of Huning s base in the same pot to provide 276 in 58% yield. The allyl ester is deprotected using palladium catalysis to give the corresponding acid 277, which is... 

Examples of organooxasilacycloalkanes have been presented by Makarova and co-workers.43 2,8-Dichloro-2,4,4,6,6,8,10,10,12,12-decamethyl-5-carbacyclohexasiloxane, 4,7-dichloro-2,2,4,7-tetramethyl-l,3-dioxa-2,4,7-trisila-cycloheptane, and 4,8-dichloro-2,2,4,8-tetramethyl-l,3-dioxa-2,4,8-trisilacyclooctane were prepared for the first time by the heterofunctional condensation of l,l,7,7-tetrachloro-l,3,3,5,5,7-hexamethyl-4-carbatetrasiloxane with... 

Dichloro-I, 2,3,4-tetramethyl-CYCLOBUTENE, 46, 34 o,a-Dichlorotoluene, condensation with ethyl cyanoacetate, 48, 54 Dicyclohexylcarbodiimide in oxidation of cholane-24-ol with dimethyl sulfoxide and pyridinium trifluor-oacetate, 47, 25... 

Treatment of 5,6-dichloro-2,3-dimethyl- -benzoquinone with sodium sulfide followed by oxidation with nitric acid yields the thianthrene derivative (60). Sulfur extrusion from 60 with peracetic acid leads to 2,3,7,8-tetramethyl-l,4,6,9-dibenzothiophene tetrone (61) (overall yield 57%). ... 

X-Ray diffraction studies of complexes of 2,9-dimethyl-1,10-phenanthroline (cf. e.g. Preston and Kennard33 and Power34) and 2,4,7,9-tetramethyl-l,10-phenanthroline (e.g., Canty and Gatehouse35) and the overcrowded molecule, l,10-dichloro-3,8-dimethyl-4,7-phenanthroline,36 have also been determined. 

The 119Sn chemical shifts for the distannoxanes provide evidence for the existence of a dimeric ladder structure [9] in solution. (73) The tetrabutyl-dichloro- and -dibromo-distannoxanes and tetramethyl-bis-(trimethylsiloxy)distannoxane show two well-resolved u9Sn signals... 

Spirocompound 43 was prepared in low yields (20%) by salt metathesis reaction of tetrakis(lithiomethyl)silane with l,2-dichloro-l,l,2,2-tetramethyl disilane <20000M4223>. 

The bathochromic effect of methyl groups is small (about 2 nm). An additional band in the region 305-345 nm (log e 3.48-3.76) was found in the spectra of the [b]-series and the benzo derivative. Only the thieno[b]tro-pylium salts exhibit a third band at 338-346 nm (log s 3.57-3.78). Dichloro-dimethyl compound 337b, compared with the tetramethyl derivative 337a, shows a bathochromic shift of about 10 nm (67JOC1610). 

Reaction of dichloro(2,2,Ar,A-tetramethyl-3-buten-l-amine)palladium-(II) with CH2N2 gives the carbene insertion product, a-chloro-A-(chloromethyl)-c/,c-(2,2,jV,7V-tetramethyl-3-buten-l-amine(palladium(II)) (56), together with analogous ethoxymethyl and methyl complexes (127). 

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