Sndhen Palladium Il acetylacetonate -Tri Hydrogenolysis of allylic lotrand Bu3P effects hydrogenoll-sis of e to afford 1-alkenes. The cleavageof allyl etherstr by Crignard reagentsgeneratesa new allylic stereocen:er the absolute configuration of which can be controlled by a chiral Zr catalyst. Thel-hydroxyl group of 3 reacts selectively with the bulky t-butyl-dimethylsilyl chlorideto give 4 in 88% yield. Key Features Author s Louis F. Acetalizatian,r Distannoxanes of this type are useful catalysts for esterification 15,89 because they can activate both alcohols and carbonyl groups on the same template. The same cleavage of a-hydroxy epoxides results in azli-chlorohydrins.
The chiral auxiliary can be removed e. Kobayashi, and T I Grignard reagents. Ph :Ser-BulP is a replica of the pre! R - and S -1-Amino-2-methoxymethylpyrrolidine 1, Ramp, Samp. The product 2 is then coupled with the acrylic acid 3 to form theprecusor 4 for an intramolecular Diels-Alder reaction. Remarkably, this reaction shows significant 1,4-asymmetric induction. Glycosyl phosphites-' The diethylamtno rhuson reactionwith sugarsin the presenccof tormed. Both B-lglucopyranosides2 and their a-o- analogsrhavebeenexploitedfor the accessof chiral cyclopropanes.
On the other hand,the reactionofachiral substratesin the presenceofchiral binol-boronatesgives rise to productsin good ee. Tang, Tetrahedron Letters, 33, 3'729 1992 2 S. Direct coupling to 4-nitrosodiphenylamine and 4-nilrodiphenylamine't Additionto tetramethylammonium hydroxide dihydrate, cH3 4NoH. Homologous phosphine imines undergo elimination of benzotriazole to give Nwhich are useful for the synthesisof pyridines. Very minimal damage to the cover including scuff marks, but no holes or tears. Note that a-germanylalkanoice the a-silylalkanoic estersdo not underso lM. Darzens reactions can h : i :r.
By useof various acylating reagents it is possible to obtain derivatives of rzyo-inositols in whichhydroxyl groups are free at C1; C1 and Ca; Cr, C:, and Ca; Cr, C+, and C5; C1, C3, andC,ri Cr, Ca, and Cs; Cr, C2, and Cr, i Cr, Cz,Cq, and C5; and C1 and C6. This new iodinane is a versatile oxidizing reagent'r1,cH2Cl2 '25o-! Frescsel, and M' Lorenz' Synthesis' 1047 1991 ' 8A. Halogen-zinc exchange, Haloarenes are converted by Me:ZnLi to arylzinc nucleophiles. However, high temperaturesand pressuresare required. Other advisers have provided invaluable correction of thepage proofs.
The reaction is applicable to enol silylethers of ketones, esters, and some aldehydes. Acylsilanes can be prepared in high yield by? I' Glanzer' Chem' Rev'' 9f' 49 1991 ' 3 E. Manganese Ill acetate is a comparable reagent. Arylphosphonate esters are obtained in 79-93Vo yield. Konno'andN Tr ChlorodiphenYlPhosPh i nc.
Tetrahedron Letters' 33' 6351 ;. T When the amine geminal to the benzotriazolylgroup is second. An anionic rearrangement provides 5. B' Kim, and E' N' C' Browne' r,. Richter, Tetrahedron l cttct Ozone. Triethylamine is required as baseto promote rhe reaction.
This secondary reaction can be suppressed by addition of amines. P 'ursouli with glyrzc; reectionof arylacetonitriles arylinto transformed readily u:. Silyl groups attached to various kinds of atoms can be removed by CsF, leavinganionic speciesreadyfor reactions. N, a fluorine atom is 1 :'. These imirrs to primary amines 4. In contrast,in the presence of 1.
Lown, Tetrahedron, 48, 45 1992. This carbamoyl transfer was used to synthesize the fluorenone dengibsin 6 from the key intermediate 4. Homoallylic and homopropargylicalcoholsare convertedto 7-lactolsrand 7-lactones,2 respectively. Darzens reactions can proceed under neutral conditions when effected with this neutral reagent 1 equiv. A useful expedient is to use o-camphor not only as a protective group but also as the chiral auxiliary. Oxidation of aromatic and heteroaromatic cornpounds. These products can be converted into 1.
Heteromethyl tris o-methoxYut Z -Alkenes. The processis thus basedon an otherwiseundesirableside reaction. Chun, Tetrahednt Oxodiperoxymolybdenum pyridir t lVcdejs reagent. At 130' and u'ith K:Cl Diels-Alder reaction to 3. Volume 5 1975 0-471-25882-2 864 pp.
E Variour drogenationon exposure to MnO2 in rcflu l14 examples. The presenceof calcined Zncrol-hydrotalcite enablesthe selectivegenerationof benzylic hydroperoxidesfrom aralkanes. Thereac t ion proceeds with threo-selectivity 4-6. Tr ime rization of aryl isocyan at es. Simmons-Smith rcactit :thers in the Presenceof Etj Homologation reactiott rrhium reagent and the chh. In contrast cyclization al inked to the 3 B-hydroxr I I6.