Synthesis of perfragilin A, B and some analogues

Synthesis of the cytotoxic isoquinoline quinone perfragilin A, an improved synthesis of perfragilin B and preparation of some analogues of both these compounds are described. Cytotoxicity evaluation of a number of the products is reported. The regioselectivity in Diels-Alder reactions of differently substituted benzoquinones with 2-aza-1,3-bis(t-butyldimethylsilyloxy)-1,3-butadiene is described.     

2-Oxobenzo[h]chromene: a novel entry for the synthesis of functionalized angular polycyclic azaarenes

An efficient and short synthesis of (5,6-dihydrobenzo[h]pyrido[2,1-b]quinazolin-2-ylidene)acetonitriles, (5,6-dihydrobenzo[h]pyrazino[2,1-b]quinazolin-2-ylidene)acetonitriles and (5,6-dihydrobenzimidazo[1,2-b]benzo[f]isoquinolin-7-yl)acetonitriles in good yields is delineated through base catalyzed ring transformation of 4-(piperidin-1-yl)-2-oxo-5,6-dihydro-2H-benzo[h]chromene-3-carbonitriles with 2-amino-pyridine, 2-aminopyrazine and (imidazo-2-yl)acetonitrile.     

Synthesis of 1,2,3,9a-tetrahydro-9H-imidazo[1,2-<Emphasis Type="Italic">a</Emphasis>]indole-2-thione and 1,5,6,10b-Tetrahydroimidazo[2,1-<Emphasis Type="Italic">a</Emphasis>]-isoquinoline-2(3H)-thione derivatives

Thionation of 1,2,3,9a-tetrahydro-9H-imidazo[1,2-a]indol-2-one derivative with Lawessons reagent in boiling toluene afforded 1,2,3,9a-tetrahydro-9H-imidazo[1,2-a]indole-2-thione derivative. Alkylation of the latter with ethyl iodide in DMF in the presence of a strong base gave 2-ethylthio-9,9,9a-trimethyl-9,9a-dihydro-3H-imidazo[1,2-a]indole. 1,5,6,10b-Tetrahydroimidazo[2,1-a]isoquinoline-2(3H)-thiones were synthesized by thionation of the corresponding carbonyl substrates.Published in Khimiya Geterotsiklicheskikh Soedinenii, No 11, pp. 1695–1700, November, 2004.     

Symmetrical and Unsymmetrical Bis-1,1′-(3,4-dihydroisoquinolines)

3,3,-Dialkyl-1-cyano-3,4-dihydroisoquinolines were prepared by Beckmann defragmentation of ethyl α-(3,3-dialkyl-3,4-dihydroisoquinol-1-yl)-α-hydroximinoacetates and they take part in a Ritter reaction to form substituted bis-1,1′-(3,4-dihydroisoquinolines).__________Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 558–563, April, 2005.     

Some new aspects of benzyne and radical mediated cyclisations

KNH₂/NH₃ cyclisations of some alkoxy substituted arylhalides proceed in poor yields. This shortcoming may be overcome by the use of LDA/THF to effect the ring closure which may occur through benzyne or radical intermediates. Besides ortho halogenated dihydroanils and amides, the cyclisation of the benzylamine Schiff bases also provides a convenient route to isoquinoline alkaloids.     

Two New Isoquinoline Alkaloids from Carduus crispus

Two new isoquinoline alkaloids: carcrisine A and B, have been isolated from the whole plant of Carduus crispus L.. Their structures were elucidated by chemical and spectroscopic methods.     

ELECTRON SPIN RESONANCE STUDY OF PHOSPHORANYL RADICALS I. INFLUENCE OF STERIC AND ELECTRONIC EFFECTS ON RADICAL FORMATION IN SOLUTION

Abstract

An electron spin resonance study of phosphoranyl radicals, generated by u.v. irradiation of solutions containing a trialkylphosphite and a dialkylperoxide, enabled us to examine the influence of steric and electronic factors on radical formation. It was demonstrated that the influence of steric factors, such as α- or β-branching of the alkyl groups, on the magnitude of radical formation was present in both trialkyl- and methyldialkylphosphites, but not in dimethylalkylphosphites. Furthermore, the study of additional hetero atoms in the alkyl ligand of the dimethylalkylphosphites clearly revealed the influence of the gauche-effect. It was demonstrated that the presence of the gauche-effect, which causes a conformational preference in which a larger steric hindrance is produced, resulted in a decrease of radical formation.     

A Facile Synthesis and Crystal Structure of 1-Amino-3-(2''-methylphenyl)isoquinolin Hydrochloride

The title compound(C16H15ClN2)has been synthesized by a facile self-condensation of ο-tolunitrile promoted by potassium tert-butanolate in DMPU,and its structure was characterized by 1H NMR,13C NMR,IR,UV,HRMS and X-ray single-crystal diffraction.The crystal belongs to orthorhombic.space group Pna21 with a=19.560(3),b=7.8500(14),c=18.428(3)(A),Dc=1.271g/cm3,Z=8,λ=0.71073(A),μ(MoKα)=0.257 mm-1,Mr=270.75,V=2829.5(8)(A)3,Hack parameter=0.12(12),F(000)=1136,the final R=0.0571 and wR=0.1445 for 2701 observed reflections with I＞2σ(I).The intermolecular N-H…Cl hydrogen bonds link the molecules into a one-dimensional chain running along axis a.     

A one-pot conversion of ortho-alkynyl benzaldehydes into indolo[2,1-a]isoquinolines

The conversion of readily available 2-halobenzaldehydes into indolo[2,1-a]isoquinolines in two operations represents a very direct entry to this class of molecules.     

Allylmetallation of benzoazaheterocycles with allylic derivatives of zinc. Synthesis of 1,4-ethano-2,3-dihydroisoquinolines and allylated heterocycles

Allylmetallation of isoquinolines, quinoline, and quinoxaline with allylic derivatives of zinc was examined for the first time. A convenient procedure was discovered and developed for the synthesis of 1,4-ethano-2,3-dihydroisoquinolines based on the reactions of isoquinolines with allylic derivatives of zinc. This multistage process involves double allylmetallation of the heterocyclic ring followed by cyclization through intramolecular carbometallation of the C=C bond. The structures of three key derivatives of 1,4-ethano-2,3-dihydroisoquinoline were established by X-ray diffraction analysis. The reactions of quinoxaline with allyl- and methallylzinc bromide proceeded stereospecifically to form trans-2,3-diallylated 1,2,3,4-tetrahydroquinoxalines. Heating of quinoline with methallylzinc bromide in THF afforded 4-methallylquinoline in nearly quantitative yield. The initially formed 1,4-metallation product underwent aromatization through elimination of HZnBr.