Syntheses of fluorescent dyes. IX. New 4-hydroxycoumarins, 4-hydroxy-2-quinolones, 2H,5H-Pyrano[3,2-c]benzopyran-2,5-diones and 2H,5H-Pyrano[3,2-c]quinoline-2,5-diones

7-Substituted 4-hydroxycoumarins (2a-e) and 4-hydroxy-2-quinolones (2f-i) have been synthesized from the appropriate phenols or anilines and were converted to the enamines 3 using triethoxymethane and aniline. Condensation of 3 with nitriles 4a-h gave substituted 2H,5H-pyrano[3,2-c]benzopyran-2,5-diones (5a-r) or 2H,5H-pyrano[3,2-c]quinoline-2,5-diones (5s-x) , which exhibit both spontaneous and stimulated fluorescence with maxima between 418 and 549 nm. The marked influence of an electron withdrawing 3-substituent in 5 is demonstrated by the fluorescence spectra of 7a,b (synthesized from 2d,e and ethyl 3-oxobutyrate), whose maxima are sharply shifted to the blue as compared with compounds 21-r.     

Eine breit anwendbare Synthese fluoreszierender kondensierter α-Pyrone

In a two step procedure and in usually good yield an -pyrone ring can be annelated to (enolized) cyclic -dicarbonyl compounds like 4-hydroxy-2-pyrones, 4-hydroxycoumarins, 4-hydroxy-2-quinolones and more complex malonylheterocycles, but also to -naphthole.In a first step the combined action of triethyl orthoformate and arylamines upon the dicarbonyl system affords the anilinomethylene derivativesB in usually high yields.B is reacted with an active methylene nitrile (like alkyl cyano-acetates) and one equivalent of a strong base (like sodium methoxide or potassium hydroxide) in a polar aprotic solvent (like dimethylformamide). Subsequent acidification with dilute aqueous acid gives the corresponding -pyroneD with yields from 18 to 84%.The reaction sequence is broadly applicable, which is demonstrated by the synthesis of a series of known (3, 7, 16, 31) and novel (10, 19, 22, 25, 28, 34) heterocyclic systems. Most of them exhibit strong fluorescence in the visible with emission maxima between 450 and 510 nm.

208. Mitt.:H. Wittmann undF. Günzl, Z. Naturforsch.33b, 1540 (1978).     

Eine neue Methode zur stereochemischen Analyse offenkettiger terpenoider Carbonyl-Verbindungen,

A New Method for the Stereochemical Analysis of Acyclic Terpenoid Carbonyl Compounds A new method for the determination of the enantiomeric and diastereoisomeric composition of terpenoid carbonyl compounds is presented. Separation of the diastereoisomeric (+)-L -diisopropyl-tartrate acetals derived from dihydrocitronellal ( 6 ), hexahydropseudoionone ( 3 ), hexahydrofarnesal ( 7 ), and hexahydro far nesy lace tone ( 4 ), the C₁₀, C₁₃, C₁₅, and C₁₈ intermediates in various syntheses of naturally occurring tocopherols and vitamin K₁, can be achieved by capillary GC on a cyanopropylsilicon-coated glass column under standardized conditions. This technique, presenting a significant improvement over existing methodologies, is considered to be particularly useful for the analysis of highly enriched samples, typically obtained by present-day asymmetric synthesis. With reproducibilities of ± 0.3%, and, therefore, safe for routine analysis, the complete Stereochemical characterization of terpenoids with 15 and 18 C-atoms bearing two stereogenic centres is performed in a single operation for the first time.     

Axially Dissymmetric diphosphines in the Biphenyl Series: Crystal structures of three new group-VIII metal complexes of (6,6′-dimethyl-1,1′-biphenyl-2,2′-diyl)bis(diphenylphosphine) ( = biphemp)

(6,6′-Dimethyl-1,1′-biphenyl-2,2′-diyl)bis(diphenylphosphine) ( = biphemp) reacts with allymetal halidesm to yeild complexes 1–3 which were transformed into the corresponding perchlorates 4–6 . The molecular structures of 4–6 were determined by X-ray analyses.     

Nucleophilic Additions to N-Glycosylnitrones. Asymmetric Synthesis of α-Aminophosphonic Acids

The hypothesis which explains the diastereoselectivity of the 1,3-dipolar cycloaddition of the N-glycosylnitrones 1 – 3 leading to the 5,5-disubstituted isoxazolidines 4 – 6 on the basis of a kinetic anomeric effect predicts that nucleophiles should add to N-glycosylnitrones with a high degree of diastereoselectivity. To test this prediction, the nucleophilic addition of lithium and potassium dialkylphosphites to the crystalline (Z)-nitrone 11 , prepared from oxime 9 and (benzyloxy)acetaldehyde has been examined. The addition of lithium phosphites gave the N-glycosyl-N-hydroxyaminophosphonates 12 – 16 (d. e. 78–92%) in high yields (Scheme 4). The addition of potassium phosphites showed a much lower diastereoselectivity. Glycoside cleavage, hydrogenolysis, and dealkylation of 12 – 16 gave (+)-(S)-phosphoserine (+)- 19 (34–45% from 9 ). Its absolute configuration was confirmed by an X-ray analysis of the N-(3,3,3-trifluoro-2-methoxy-2-phenylpropionyl) derivative 24 . Similarly, the crystalline nitrone 25 gave the N-glycosyl-N-hydroxyaminophosphonate 26 , which was transformed into (+)-(S)-phosphovaline (+)- 31 (42% from 9 ). The diastereoselectivity of the nucleophilic addition and the enantiomeric purity of (+)- 31 were determined by the analysis of the derivative 30 (d.e. 92%) and 32 (d.e. 93%), respectively. The addition of lithium diethyl phosphite to the nitrone 33 , prepared in situ, gave the N-glycosyl-N-hydroxyaminophosphonate 34 , (41%; d.e. 91%), which was transformed in (+)-(S)-phosphoalanine (+)- 37 (21% from 9 ).     

Palladium-Catalyzed Ene-Type Cyclizations of Terpenoid 1,6-Enynes

Palladium-catalyzed ene-type cyclizations of 1,6-enynes 2 yield methylidene-cyclopentane derivatives 3 . Removal of protecting groups from 3 furnishes the diols 4 and 5 , whose configurations were established by a combination of X-ray and ¹H-NMR techniques. The predominant formation of isomers 4 is discussed in the context of two alternative hypothetical mechanisms previously proposed for this type of cyclization.