Oxazoline Mediated Routes to a Unique Amino-acid, 4-Amino-13-carboxy[2.2]paracyclophane, of Planar Chirality

Planar‐Chiral Thioureas as Hydrogen‐Bond Catalysts

“…It has been demonstrated that substituents on the Pc framework -such as carboxylic acids, esters, and nitro groups, allow regioselective electrophilic aromatic substitution in the pseudo-geminal position. This position was accessed through the regioselective bromination of methyl ester S P -8, [14] obtained through the reaction of the acid chloride with methanol. The saponification of resulting bromo ester R P -9 [14] generated bromo carboxylic acid S P -10, which then served as a precursor for the Curtius rearrangement (Scheme 1).…”

“…This position was accessed through the regioselective bromination of methyl ester S P -8, [14] obtained through the reaction of the acid chloride with methanol. The saponification of resulting bromo ester R P -9 [14] generated bromo carboxylic acid S P -10, which then served as a precursor for the Curtius rearrangement (Scheme 1). The thermally generated isocyanate (from R P -11) was trapped by tert-butyl alcohol to obtain Boc-protected (Boc = tert-butoxycarbonyl) amine R P -12 in 67 % yield over two steps.…”

Synthesis of Pseudo-geminal-, Pseudo-ortho-, andortho-Phosphinyl-oxazolinyl-[2.2]paracyclophanes for Use as Ligands in Asymmetric Catalysis

“…Following previously described syntheses of 1 and similar derivatives, 24,25,27,28 racemic carboxylic acid 4 was converted to the acid chloride, reacted with L-valinol and cyclized under Bryce's conditions 29 to…”

“…24 and the mixture heated at reflux for 16 h. The reaction mixture was washed with saturated NaHCO 3 solution (2 × 10 mL) and brine (10 mL 2, 138.6, 136.6, 136.0 (C-15), 135.9 (C-5), 134.9 (2 C, s, C-8, 16), 132.9 (C-12) = 9.8), 136.0, 135.7, 135.3, 134.7, 134.2, 133.8, 133.0, 132.83, 132.76, 130.9 The reaction mixture was allowed to warm to rt and stirred for 18 h with slow bubbling of CO 2 . The mixture was extracted twice with water (1 L, 500 mL) then aq NaOH solution (6 M, 50 mL).…”

The Synthesis of Pseudo‐Geminal, Pseudo‐Ortho and Ortho Hydroxy‐oxazolinyl[2.2]paracyclophanes for Use as Ligands in Asymmetric Catalysis

“…The pseudo-geminal substitution pattern was established by directed bromination of oxazoline 4 (Scheme 1), [19,20] a technique discovered many years ago by Reich and Cram. [21] The resulting bromides 5 were converted to the phenols 1 by lithiation, quenching with BA C H T U N G T R E N N U N G (OMe) 3 and oxidation with basic H 2 O 2 .…”