Silanes nitro compounds

An impressive application is the total synthesis28 of the anti-tumour antibiotic (+)-macbecin I 163. The amide disconnection is obvious and the decision to make the amino quinone from an aromatic nitro compound 164 sensible. Less obvious is the synthon 165 as the anion at C-14 could be an allyl silane but the further disconnections of 165 all correspond to allyl silane chemistry. 

DeShong (Scheme 20). Thus, reaction of nitrones with vinyl silanes followed by reduction provides Peterson - type intermediates which can then be eliminated to either Z- or E-products. Homoallylic amines were also prepared using allylsilane in the initial cycloaddition. Substitution reactions of allylic nitro compounds have received considerable attention and some examples are outlined in Scheme 21. In each case, examination of the regiochemistry of the reaction was of paramount concern, the results using palladium being superior to the SnCl mediated process. Allylic sulphides constitute yet another group of... 

Triphenylsilyl ethers are typically prepared by the reaction of the alcohol with triphenylsilyl chloride (mp 92-94 °C) and imidazole in DMF at room temperature. The dehydrogenative silylation of alcohols can be accomplished with as little as 2 mol% of the commercial Lewis acid tris(pentaf1uorophenyl)borane and a silane such as triphenylsilane or triethylsilane [Scheme 4.98]. Primary, secondary, tertiary and phenolic hydroxyls participate whereas alkenes, alkynes, alkyl halides, nitro compounds, methyl and benzyl ethers, esters and lactones are inert under the conditions. The stability of ether functions depends on the substrate. Thus, tetrahydrofurans appear to be inert whereas epoxides undergo ring cleavage. 1,2- and 1,3-Diols can also be converted to their silylene counterparts as illustrated by the conversion 983 98.4. Hindered silanes such as tri-... 

Nitro compounds from silanes and germanes Partial nitrodesilylation s. 16, 515... 

Different y- and d-aminofrmctionalized ethers, amines and silanes 169 are obtained from aUcenes 168. Branched derivative is the main product obtained when X=OR, NR. The alkylation of the primary amines leading to secondary or tertiary amines can be controlled by the alkene/amine ratio [100]. Nitro derivatives can be used instead of amines, since they are rednced to amines in the reaction conditions [101]. Selective monoalkylation or dialkylation of nitro compounds is achieved depending on the alkene/nitro compound ratio. 

Jeffrey C. PeUetier of Wyeth Research, Collegeville, PA has developed (Tetrahedron Lett. 2007, 48,7745) a easy work-up Mitsunobu procedure for the conversion of a primary alcohol such as 1 to the corresponding primary amine 2. Shlomo Rozen of Tel-Aviv University has taken advantage (J. Org. Chem. 2007, 72, 6500) of his own method for oxidation of aprimary amine to the nitro compound to effect net conversion of an amino ester 3 to the alkylated amino ester 5. Note that the free amine of 3 or 5 would react immediately with methyl iodide. Keith A. Woerpel of the University of California, Irvine has uncovered (J. Am. Chem. Soc. 2007,129,12602) a Cu catalyst that, with 7, effected direct conversion of sUyl ethers such as 6 to the aUyl silane 8. An Ag catalyst gave 9, which also shows arllyl silane reactivity. Biswanath Das of the Indian Institute of Chemical Technology, Hyderabad has established (Tetrahedron Lett. 2007, 48, 6681) a compact procedure for the direct conversion of an aromatic aldehyde such as 10 to the benzylic halide 11. This will be especially useful for directly generating benzyhc hahdes that are particularly reactive. 

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