SYNTHESIS 2,4,6,2 ,4 ,6 -hexamethyl-,

Epoxyfarnesol was first prepared by van Tamelen, Stomi, Hessler, and Schwartz 4 using essentially this procedure. It is based on the findings of van Tamelen and Curphey5 that N-bromosuccinimide in a polar solvent was a considerably more selective oxidant than others they tried. This method has been applied to produce terminally epoxidized mono-, sesqui-, di-, and triterpene systems for biosynthetic studies and bioorganic synthesis.6 It has also been applied successfully in a simple synthesis of tritium-labeled squalene [2,6,10,14,18,22-Tetracosahexaene, 2,6,10,15,19,23-hexamethyl-, (all-E)-] and squalene-2,3-oxide [Oxirane, 2,2-dimethyl-3-(3,7,12,16,20-pentamethyl-3,7,ll,-15,19-heneicosapentaenyl)-, (all-E)-],7 and in the synthesis of Cecropia juvenile hormone.8... 

Previous studies by Sorokin with iron phthalocyanine catalysts made use of oxone in the oxidation of 2,3,6-trimethylphenol [134]. Here, 4 equiv. KHSO5 were necessary to achieve full conversion. Otherwise, a hexamethyl-biphenol is observed as minor side-product. Covalently supported iron phthalocyanine complexes also showed activity in the oxidation of phenols bearing functional groups (alcohols, double bonds, benzylic, and allylic positions) [135]. Besides, silica-supported iron phthalocyanine catalysts were reported in the synthesis of menadione [136]. 

Durene, pentamethyl benzene and hexamethyl benzene have usually been prepared from benzene or one of its methylated derivatives by the Friedel-Crafts synthesis.1 Durene has been made from bromine derivatives of methylated benzenes by the Fittig reaction.2 It has also been obtained in 20 per cent yield by passing methyl alcohol and acetone vapors over heated alu-... 

Our research group [48] has also been interested in the synthesis of ningalin B and our route to ningalin B hexamethyl ether is presented in Scheme 16. 

Iwao and Ishibashi [37] have utilized their methodology depicted in Scheme 13 for the preparation of ningalin B hexamethyl ether (91) with compound 71 functioning as the key precursor for this relay synthesis. This strategy appears to be very flexible for a wide variety of pyrrole natural products. 

The third way for the synthesis emanates from 2-methylamino-5-chlorobenzophenone (5.1.5), which is acylated by chloracetic acid chloride, forming 2-chloracetylmethylamido-5-chlorbenzophenone (5.1.6). Reaction of this product with hexamethylenetetramine replaces the chlorine atom in the chloracetyl part of the molecule, giving a hexamethyl-enetetramino derivative of 2-aminoacetyhnethylamido-5-chlorbenzophenone, which upon hydrolysis in an hydrochloric acid ethanol solution undergoes cyclocondensation and gives diazepam (5.1.2) [6,7]. 

Nanocomposite Si-C-N ternary UFPs have been synthesized for aiming at improving the properties of the final powders, increasing safety, and lowering the production cost. In the laser-induced synthesis, many gaseous mixtures are used as reactants, such as hexamethyl-disilazane ((CH3)3SiNHSi(CH3)3) (68,69), methyl-amine (CH3NH2), and dimethylamine ((CH3)2NH) (70-72). 

A number of higher thioketones have teen prepared by pyrolysis of hexa-substituted trithianes (40, 41). These trithianes were made by methods already discussed for synthesis of hexamethyl-s-trithiane. Those investigated include compounds of the structure... 

A key step in one route to the synthesis of hexamethyl Dewar benzene is the cycloaddition of 2-butyne to tetramethylcyclobutadiene (stabilized by A1 cation). Using the parent compounds (no methyls), develop a Woodward-Hoffmann orbital correlation diagram for the reaction and determine whether the reaction is thermally allowed. 

Scheme 3. Synthesis of 2,6-m-diphenyl-hexamethyl-cyclotetrasiloxane and its trows-isomer...

Demethylation by sulfuric acid can be successfully extended to certain organofunctional methyldisilanes. For instance, (chloromethyl)penta-methyldisilane easily undergoes demethylation under similar conditions to give l-(chloromethyl)-2-chloro(or fluoro)tetramethyldisilane upon treatment with an ammonium halide, in good yield (120). Moreover, this method is still satisfactory for synthesis of l,3-dichloro(or difluoro-)hexamethyl-trisilane (III), which is obtainable in 40% (or 55%) yield from octamethyl-trisilane (in this case, demethylation occurs concurrently at both the 1- and 3-silicon atoms, unlike the demethylation of hexamethyldisilane) (102,106, 107). 

Each of these alkylating agents is readily available and each has a characteristic and well-known reactivity. The successful preparation of hexamethyl tungsten is one fairly recent example of the necessity of having a number of alternative reagents for a given synthesis (2). 

The synthesis of alkali metal 1,4,2-diphosphastibolides parallels that of the 1,4,2-diphosphaarsolides 18 and 19. It is however regiospecific and no 1,2,4-isomer is formed. For the synthesis, a DME solution of lithium bis(trimethylsi-lyl)antimonide 31 (M = Li) is treated with 3equiv of the phosphaalkene 29. In the course of the reaction, the phosphaalkene 29 is converted to the phosphaalkyne 30 via the base-catalyzed elimination of hexamethyl disiloxane (Scheme 7). Alternatively, the phosphaalkyne 30 can be used directly in place of the phosphaalkene. After addition of TMEDA or 12-crown-4, the lithium 1,4,2-diphosphastibolide 22 (M = Li(TMEDA)2) or Li(12-crown-4)2 is isolated <1997JOM291>. 

The present Chapter discusses synthesis and studies of carbosiloxane copolymers containing flexible dimethylsiloxane and decaorganotricyclodecasiloxane fragments in the backbone [23, 24], For the purpose of synthesizing carbosiloxane copolymers, hydride addition of a,ra-dihydridedimethylsiloxane to 1,3-divinyl-1,3,9,9,11,11-hexamethyl-... 

Anhydrous lanthanide adducts with dimethyl formamide (DMF) [4], dimethyl sulphox-ide [5] (DMSO) and hexamethyl phosphoramide [6] may be used for the synthesis of anhydrous complexes as long as their solvation does not interfere with the preparative reaction [7],... 

Trimethylenecyclopropane, [3]radialene (169), which is one of the benzene isomers and the smallest member of the radialene family, is characterized by a cyclic arrangement of cross-conjugated Ti-electron systems. The synthesis and properties of radialenes have been reviewed recently by Hopf and Maas The C—C and C=C bond lengths in 169,1.453 (3) and 1.343 (3) A, determined by are similar to those in its hexamethyl derivative... 

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