Concise synthesis of quinazoline alkaloids, luotonins A and B, and rutaecarpine

The total synthesis of luotonin A was achieved in excellent yield by using a Pd-assisted biaryl coupling reaction of N-(bromoquinolinyl)methylquinazolinone with Cy₃P and KOAc. The successive treatment of luotonin A with NBS and aq. AgNO₃ gave luotonin B in good yield. Although the Pd-assisted coupling reaction of N-(2-bromoindolyl)ethylquinazolinone with Cy₃P and KOAc yielded rutaecarpine in poor yield, N-acetate under the same reaction conditions yielded the desired rutaecarpine directly in excellent yield.     

A general nickel-catalyzed hydroamination of 1,3-dienes by alkylamines: catalyst selection, scope, and mechanism

A simple colorimetric assay of various transition-metal catalysts showed that the combination of DPPF, Ni(COD)(2), and acid is a highly active catalyst system for the hydroamination of dienes by alkylamines to form allylic amines. The scope of the reaction is broad; various primary and secondary alkylamines react with 1,3-dienes in the presence of these catalysts. Detailed mechanistic studies revealed the individual steps involved in the catalytic process. These studies uncovered unexpected thermodynamics for the addition of amines to pi-allyl nickel complexes: instead of the thermodynamics favoring the reaction of a nickel allyl with an amine to form an allylic amine, the thermodynamics favored reaction of a nickel(0) complex with allylic amine in the presence of acid to form a Ni(II) allyl. The realization of these thermodynamics led us to the discovery that nickel and some palladium complexes in the presence or absence of acid catalyze the exchange of the amino groups of allylic amines with free amines. This exchange process was used to reveal the relative thermodynamic stabilities of various allylic amines. In addition, this exchange reaction leads to racemization of allylic amines. Therefore, the relative rate for C-N bond formation and cleavage influences the enantioselectivity of diene hydroaminations.     

Nickel-catalyzed acylstannylation and alkynylstannylation of 1,2-dienes

Carbostannylation of 1,2-dienes using acyl- and alkynylstannanes was achieved by means of nickel catalysis. In particular, acylstannylation of 1,2-dienes could be carried out with bis(1,5-cyclooctadiene)nickel [Ni(cod)₂] and acylstannanes to give selectively α-acylmethyl(vinyl)stannanes. The reaction was also applicable to acylstannanes prepared in situ by protonolysis of α-alkoxyalkenylstannanes or by reactions of α-silyloxyvinylstannanes with aldehyde acetals. For alkynylstannylation, a combination of Ni(cod)₂ and 1,3-bis(diphenylphosphino)propane (dppp) was found to be effective to afford α-alkynylmethyl(vinyl)stannanes, whereas the Ni(cod)₂-1,3-bis(dimethylphosphino)propane (dmpp) catalyst switched the regioselectivity to give (Z)-α-alkynylmethyl(alkenyl)stannanes. The acylstannylation products were successfully converted into various conjugated or unconjugated enones by a combination of cross-coupling and NaH-catalyzed isomerization. The alkynylstannylation products were transformed by cross- or homo-coupling reactions to various enynes or 2,3-bis(alkynylmethyl)-1,3-dienes, versatile precursors for variously substituted polycyclic compounds.     

The ion-pair formation between dodecylsulfate and ammine-complexes of copper(II), nickel(II), zinc(II), palladium(II) and platinum(II), and the extraction behavior of the ammine-complexes by using sodium dodecylsulfate

A micellar solution of sodium dodecylsulfate (SDS) exhibits the property of being separated into two phases due to a temperature change or the addition of salts. The ammine-complexes of copper(II), nickel(II) and palladium(II) reacted with the dodecylsulfate anion to form the corresponding ion-pair, and were extracted into the SDS gel phase. The SDS plays the roles of a pairing-ion for the ammine-complexes and of an extraction medium. The ion-pair extraction mechanism was investigated; the extractability of metals was given by the function of the solubility products of the ion-pairs. This method was applied to the mutual separation of Ni(II)/Cu(II) and Pd(II)/Pt(II). The driving force for the extraction was an electrostatic interaction between the cationic complex and the surfactant anion. The use of the SDS gel as ion-exchanger is also expected.     

Synthesis of nylon 6–clay hybrid by montmorillonite intercalated with ϵ-caprolactam

It was found that montmorillonite was intercalated with ?-caprolactam. X-ray diffraction revealed that the chain axes of the ?-caprolactam were parallel to the montmorillonite plates. The intercalated montmorillonite was swollen by molten ?-caprolactam at 200°C. ?-Caprolactam and 6-aminocaproic acid (accelerator) were polymerized with the intercalated montmorillonite at 260°C for 6 h, yielding a nylon 6-clay hybrid. X-ray diffraction and transmission electron micrography revealed that the silicate layers of the hybrid were uniformly dispersed in the nylon 6 matrix. Mechanical properties of the hybrid were improved. The strength and the modulus of the hybrid increased compared with the previously reported nylon 6 clay-hybrid (NCH) synthesized by montmorillonite intercalated with 12-aminolauric acid. The heat distortion temperature (HDT) of the hybrid was 164°C, which was 12°C higher than that of NCH. © 1993 John Wiley & Sons, Inc.     

Occurrence of the cis-peptide in gaseous N-methylformamide as revealed by rotational structure in its infrared spectrum

In the 0.12 cm^?1 resolution infrared absorption spectrum of gaseous N-methylformamide, a progression of peaks with a spacing of about 2.6 cm^?1 has been found in the 610-540 cm^?1 region. This is assignable to a conformer with the CO and NH bonds cis to each other.     

Novel,Complex Flavonoids from Mallotus philippensis (Kamala Tree)

One new flavanone, 4′‐hydroxyisorottlerin ( 2 ), and two new chalcone derivatives, kamalachalcones C ( 3 ) and D ( 4 ), were isolated from Mallotus philippensis (kamala tree). The largest compound ( 4 ; M_r 1098 g/mol) was shown to possess a unique, fused‐ring system made of two hydroxy‐chalcone units, giving rise to eight fused benzene/pyran units. From the same plant, the following six known compounds were also isolated: kamalachalcone A ( 5 ) and B ( 6 ), isoallorottlerin ( 7 ), isorottlerin ( 8 ), 5,7‐dihydroxy‐8‐methyl‐6‐prenylflavanone ( 9 ); 6,6‐dimethylpyrano(2″,3″: 7,6)‐5‐hydroxy‐8‐methylflavanone ( 10 ), and rottlerin ( 1 ). The structures of the new compounds were confirmed by in‐depth spectral analyses, including 2D‐NMR techniques, and the full ¹³C‐NMR assignments of the known flavanones 1 and 7 – 10 are published for the first time.     

Through-space electronic interactions of [2.2]metacyclophane benzyl cations

The hydrolysis of 8-bromomethyl[2.2]metacyclophanes 3 to the corresponding 8-hydroxymethyl derivatives 4 was carried out in 83% aqueous dioxane solution at 25°C. Substituent effect through space on the rate of the hydrolysis of bromomethyl groups attached on the opposite aromatic ring was first found in this investigation. Interestingly, the introduction of the substituents at the internal position 16 tends to enhance the hydrolysis reaction rate 10–100 times. It was found also that the stabilization by both the direct through-space cation-π-interaction and the interaction through the intra-annular 8,16-position are possible in the [2.2]metacyclophane 8-benzyl cations. The good correlation with log(K/K_H) and σ_p ⁺ was observed for the hydrolysis of internally unsubstituted 5-bromomethyl[2.2]MCPs 7, in which the direct through-space cation-π-interactions are not possible. TiCl₄ and Nafion-H, a perfluorinated resinsulfonic acid, catalysed Friedel-Crafts benzylation of benzene and substituted benzenes with 8-bromomethyl- and 8-hydroxymethyl[2.2]metacyclophanes to afford 8-benzyl[2.2]metacyclophanes is described. A high substrate and positional selectivity were observed in the present benzylation reaction quite different from those obtained from the benzyl bromide and benzyl alcohol. The benzyl cation intermediate stabilized by the through-space electronic interaction among the opposite benzene ring was first demonstrated in the benzylation of [2.2]metacyclophane systems. The mild and selective transannular reaction attributable to the highly strained character of [2.2]metacyclophane skeleton and the increased stabilization of the 5-benzyl cation intermediate arising from the electronic interactions among the opposite benzene ring through the intra-annular 8,16-positions was also observed.     

Anomalous decrease in lamellar spacing by shear flow in a nonionic surfactant/water system

We study the effects of shear flow on the structure of a lamellar phase in a C16E7 [hepta(oxyethylene glycol)-n-hexadecyl ether]/water system (40-55 wt % of C16E7) at 70 degrees C using small-angle neutron scattering in the range of shear rate of 10(-3)-30 s(-1). At the shear rate 0.1-1 s(-1), the repeat distance (d) is decreased significantly (down to about 40% of d at rest in the most significant case) and discontinuously with increasing shear rate. With the further increase in the shear rate, d increases through a sharp minimum (referred to as d*). Such a shear rate dependence of d is obtained for all the principal orientations of lamellae. As the concentration of C16E7 decreases from 55 to 40 wt %, d increases from 6.5 to 8.5 nm at rest whereas d* remains almost constant (approximately equal to 5 nm). Moreover, d* is found to be almost equal to the thickness of bilayers obtained from the line shape analysis of small-angle X-ray scattering at rest. The results strongly suggest that the water layer is excluded by shear flow and that the lamellar phase segregates into surfactant-rich and water-rich regions, although these regions do not reach macroscopic size.     

Functional monomers and polymers. CXXXII. Template polymerization of methacrylamide derivatives containing nucleic acid bases

Free-radical polymerizations of methacrylamide derivatives containing nucleic acid bases were studied in the presence of the polymethacrylamide having complementary nucleic acid bases as template polymers. The rate of the polymerization did not show remarkable difference in the presence or the absence of the template polymer. A stable polymer complex, however, was precipitated from the polymerization system, and was found to be different in a thermal analysis from the polymer complex which was obtained by mixing of the complementary polymers in solution. Free-radical copolymerizations in the presence of the template polymers also supported the template polymerization.