Lithiierung in α‐Stellung zum N‐Atom von Triphenylacetamiden aus cyclischen sekundären Aminen. Umlagerung metallierter Triphenylacetamide unter 1,3‐Verschiebung der Carbamoylgruppe

Abstract

Lithiation in α‐Position to the N‐Atom of Triphenylacetamides from Cyclic Secondary Amines. Rearrangements of Metalated Triphenylacetamides by 1,3‐Shift of Carbamoyl Groups The reagents 2 ‐ generally available by lithiation of the triphenylacetamides 1 ‐ react with non‐enolizable carbonyl compounds and benzyl halide (s. Tables 1 and 2, and products 3). The limits of thermal stability of metalated triphenylacetamides above 0° are caused by a 1,3‐shift of the carbamoyl group into the o‐position of one of the benzene rings (s. 2b → 4 and 8a → 10). The barriers to rotation around the amide bonds of four triphenylacetamides are ca. 16 kcal/mol (s. 1b–e in Table 1).

o‐DPPB‐Directed Copper‐Mediated and ‐Catalyzed Allylic Substitution with Grignard Reagents

“…All temperatures quoted are uncorrected. The following compounds were prepared following literature procedures: ortho-Diphenylphosphanylbenzoic acid (o-DPPBA), [28] benzhydrylbenzoic acid, [29] (AE )-(E)-1-phenyl-3-penten-2-ol, [30] cyclohexyl-2-propene-1-ol, [31] (E)-3-hydroxy-oct-4-enoic acid tert-butyl ester, [32] (E)-3-hydroxy-5-phenyl-pent-4-enoic acid tert-butyl ester, [33] 2,5-dimethyl-2-hexen-4-ol, [34] 2-isopropyl-anisole (24), [35] 6-isopropylcyclohex-2-en-1-one [(AE )-25], [18] (34), temperature dependent 31 P NMR spectra. [36] …”

Tritylketone und Tritylenone. Beiträge zur sterisch erzwungenen Michael‐Addition und zur diastereoselektiven Aldol‐Addition

“…Diese vor allem auch von den Arbeitsgruppen von Beak [ll] [12], Hoppe [13] und Meyers4) entwickelte Methode der Urnpolung [15] [16] hat sich als sehr nutzlich erwiesed). Sie ist auf Pivalthioamide [2], Pivalamide [3], Triphenylacetamide [4], 2,4,6-Triisopropyl-und 2,4,6-Tri-(tert -butyl)benzamide [ 51, 2,3-persubstituierte I) ' ) 3, 4, ' ) Teilweise in vorlaufigen Mitteilungen publiziert [I]. Succinimide [6], Phosphorsaureamide [7] [lo], ' Urethane' [8] [ 131 und Harnstoffe [9] angewendet worden.…”

“…Die anderen Methoden zur Spaltung der MEM-Schutzgruppe, z. B. rnit Bis(isopropy1thio)borbromid [60], 2-Chlor-1,3,2-dithioborolan [61] oder NaI/Me,SiCI [62] 4 In einem 250 ml Metallierungskolben werden unter Ar 12,2 g (50 mmol) Ph,CH in 120 ml trockenem THF gelost, bei 0" rnit 1,l Mol-Aquiv. BuLi versetzt und wahrend 1 h bei 0"-10"metalliert.…”

“…C); 127,Ol (arom. C); 74,83 (s, C(1)); 74,09 (d, C(4)); 46,16 (d, C(3)); 26,61 ( I , C(5)); 11,60 (4); 10,19 (4 l-4-Hydroxy-3-methyl-I,1.1,4-tetraphenyl-2-butanon (1Oc CH,-C(7)); 21,55 (d, C(4)); 20,42 (q, CH,-C(4)). MS: 396 ( < 1, M ' , C28H2802), 378 (I, M' -18), 301 (l), HELVET~CA CHIMICA ACTA -Vol.…”

“…Fortunately, the blocking of the carbonyl group in trityl ketones can be run very specifically (without epimerization at the a-carbonyl center) by lithium triethylborohydride to furnish, after aqueous workup, primary alcohols and Ph3CH (Eqn. 4, products &20, 10 examples); the OH-group of the aldols 10 must be EE-, MOM-or MEM-protected (Scheme 8) before this C,C-bond cleavage can be conveyed. Some of the cleavage products are used for the chemical correlation of the aldol configuration and for the demonstration of the synthetic value of the presented method (see [21][22][23][24][25][26][27][28][29].…”