Application of commercial microwave ovens to organic synthesis.

The synthesis of insect sex phermones

Es wird in diesem Aufsatz versucht, die mechanistischen Alternativen der praparativ so fruchtbaren Diels-Alder-Reaktionen anhand der experimentellen Fakten kritisch zu diskutieren. Wenngleich sich die meisten Befunde zwanglos mit einem Synchronmechanismus vereinbaren lassen, harrt doch noch eine Reihe von Fragen der endgultigen Klarung.

Diels‐Alder‐Reaktionen: Zum Reaktionsmechanismus

Boc-L-Lysine derivatives and lysine-containing peptides bearing the electron donor 10H-phenothiazine (PTZ) or the redox chromophore tris(2,2'-bipyridine)ruthenium(II) dication ([Rub3]2+, where b is 2,2'-bipyridine) have been synthesized and characterized. SeO2 oxidation (53% yield) of 4,4'-dimethyl-2,2'-bipyridine, Ag2O oxidation (85% yield) of the monoaldehyde, complexation (96% yield) of 4'-methyl-2,2'-bipyridine-4-carboxylic acid (m-OH) with Rub2Cl2, activation (81% yield) of the acid [Rub2m-OH]2+ (PF6-)2, and condensation (83% yield) of the succinimido ester [Rub2m-OSu]2+ (PF6-)2 with Boc-Lys furnished the protected redox-chromophore module [Boc-Lys(Rub2m)-OH]2+ (PF6-)2 in 29% overall yield over five steps. The first two steps constitute the first practical synthesis of the monocarboxylic acid m-OH (45% overall yield). Also prepared were m-OSu, Boc-Lys(m)-OH, Boc-Lys(m)-OCH3, and [Rub2m-NHCH3]2+ (PF6-)2. Activation (91% yield) of 3-(10H-phenothiazine-10)propanoic acid (PTZpn-OH) and condensation (92% yield) of the succinimido ester PTZpn-OSu with Boc-Lys furnished the protected electron-donor module Boc-Lys(PTZpn)-OH (84% overall yield). The latter was used in solid-phase syntheses of two redox tripeptides, CH3CO-Ala-Lys(PTZpn)-Ala-OH and [Rub2m-Ala-Lys(PTZpn)-Ala-OH]2+ (PF6-)2. The electrochemical properties of these redox amino acids and peptides were similar to those of PTZpn-OH, [Rub2m-OH]2+ (PF6-)2, or [Rub2m-NHCH3]2+ (PF6-)2. Lys(PTZpn), [Lys(Rub2m)]2+ (PF6-)2, and other redox modules may be useful for engineering light-harvesting proteins, photovoltaic cells, and other molecular electronic devices.

Synthesis of redox derivatives of lysine and related peptides containing phenothiazine or tris(2,2'-bipyridine)ruthenium(II).

Bronsted acid-assisted chiral Lewis acid (BLA) was highly effective as a chiral catalyst for the enantioselective Diels−Alder reaction of both α-substituted and α-unsubstituted α,β-enals with various dienes. Hydroxy groups in optically active binaphthol derivatives and boron reagents with electron-withdrawing substituents were used as Bronsted acids and Lewis acids, respectively. Intramolecular Bronsted acids in a chiral BLA catalyst played an important role in accelerating the rate of Diels−Alder reactions and in producing a high level of enantioselectivity. In particular, excellent enantioselectivity was achieved due to intramolecular hydrogen bonding interaction and attractive π−π donor−acceptor interaction in the transition-state assembly by hydroxy aromatic groups in a chiral BLA catalyst.

G.I. Fray

Papers

Catalysis of the diels-alder reaction

Synthesis of d- and l-isoiridomyrmecin and related compounds

Synthesis of trans-10-hydroxydec-2-enoic acid and related compounds☆

The polymerization of propylene using an optically active catalyst system

Eine Synthese des D‐und L‐Iso‐Iridomyrmecins1)