Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Hydrazines bicyclic

Chloroquinoline (401) reacts well with potassium fluoride in dimethylsulfone while its monocyclic analog 2-chloropyridine does not. Greater reactivity of derivatives of the bicyclic azine is evident also from the kinetic data (Table X, p. 336). 2-Chloroquinoline is alkoxylated by brief heating with methanolic methoxide or ethano-lic potassium hydroxide and is converted in very high yield into the thioether by trituration with thiocresol (20°, few hrs). It also reacts with active methylene carbanions (45-100% yield). The less reactive 3-halogen can be replaced under vigorous conditions (160°, aqueous ammonia-copper sulfate), as used for 3-bromoquino-line or its iV-oxide. 4-Chloroquinoline (406) is substituted by alcoholic hydrazine hydrate (80°, < 8 hr, 20% yield) and by methanolic methoxide (140°, < 3 hr, > 90% yield). This apparent reversal of the relative reactivity does not appear to be reliable in the face of the kinetic data (Tables X and XI, pp. 336 and 338) and the other qualitative comparisons presented here. [Pg.364]

Azelastine (107) is an antiallergic/antiasthmatic agent prepared from 4-chlorobenzyl-2 -car-boxyphenylketCHie (105) by condensation with hydrazine to give the phthalazinone (106) followed by reaction of the sodium salt of this last with 2-(2-chloroethyl)-N-methylpyrrolidine (presumably involving nucleophilic ring expansion of the bicyclic quaternary salt putatively formed as a first product) to complete the synthesis [30]. [Pg.152]

Formal hydration of the double bond appeared by the hydroboration-oxidation sequence. Desymmetrization reactions with catalytic asymmetric hydroboration are not restricted to norbornene or nonfunctionalized substrates and can be successfully applied to meso bicyclic hydrazines. In the case of 157, hydroxy derivative 158 is formed with only moderate enantioselectivity both using Rh or Ir precatalysts. Interestingly, a reversal of enantioselectivity is observed for the catalytic desymmetrization reaction by exchanging these two transition metals. Rh-catalyzed hydroboration involves a metal-H insertion, and a boryl migration is involved when using an Ir precatalyst (Equation 17) <2002JA12098, 2002JOC3522>. [Pg.392]

Reductive cleavage of the N-N bond in bicyclic systems containing a ring junction hydrazine subunit presents a facile route to medium-sized heterocycles containing two or more nitrogen atoms and the subject was duly covered in CHEC-II(1996) <1996CHEC-II(8)747>. No substantial progress has been reported since its publication. [Pg.396]

The synthetically versatile 6-amino-7-cyano-l,4-dihydro-3-methyl-l-phenyl-4-thioxothiopyrano[4,3-c]pyrazole 107 has been used for the synthesis of several bicyclic and tricyclic systems. For example, reaction with hydrazine gives 108, which can be used to generate tricycles 109-111 (Scheme 8) <2002H(57)1121>. [Pg.726]

The conjugate addition of activated nitrogen nucleophiles, such as hydroxylamine and hydrazine derivatives, to a,/3-unsaturated bicyclic lactam 284 gave the corresponding /3-amino product 285 in good yield and excellent diastereoselectivity. These products can be manipulated to afford enantiopure /3-aminopyrrolidinones of potential application as conformationally constrained, substituted glutamate templates (Equation 45) <2001J(P1)2997>. [Pg.82]

This Asian species is a major agricultural pest. The pheromone has been proposed to consist of three male-specific compounds, only one of which, (Z)-exo-a-bergamotenal 150, has been reported in the literature [114]. The racemic compound was synthesized starting from farnesoic acid chloride 146 (Scheme 25) [114]. Thus, the vinyl ketene prepared from acid chloride 146 underwent 2+2 cycloaddition to give bicyclic ketone 147. The ketone function was removed by reaction with hydrazine followed by treatment of the resulting hy-... [Pg.82]

Bicyclic hydrazines have also been ring-opened using 7t-allyl chemistry. Treatment of meio-bicyclic hydrazine 88 with a chiral Pd complex in the presence of phenol provides the allyl phenyl ether 89 in good yield and moderate enantios-electivity ... [Pg.288]

The scope of electrophiles was explored with malonates and p-ketoesters, providing chiral amine adducts in high yield and enantioselectivities (Scheme 57) [109]. Addition of cyclic P-ketoesters was also explored with hydrazines, providing cyclic and bicyclic chiral amines with quaternary centers in high enantiomeric ratios (Scheme 58). [Pg.183]

The bicyclic meso-ionic 3-oxo-l,2,4-triazolo[4,5-a]pyridines (206) have been prepared by the following methods (i) the reaction of the hydrazines (207, X = H) with phosgene, (ii) heating the amide (207, X = CONH2) or the carbamate (207, X = COjEt), and (iii) alkylation or acylation of 3-oxo-l,2,4-triazolo[4,5-a]pyridine (208). The isomeric meso-ionic 2-oxo-l,3,4-triazolo[4,5-a]pyridines (209) are formed from the carbamoyl chlorides (210) and sodium azide. ... [Pg.44]

There are also many other methods published based on hydrazines. Emphasis in this section is put on new synthetic methods and new examples/adaptations of known methodologies with a broad scope. Methods to prepare very specific bicyclic or polycyclic 1,2-diazines have therefore not been incorporated. [Pg.80]

Two further unusual examples involve a different bicyclic system and an acyclic system as precursors. In the first instance, use is made of the reactivity of a pyrrolo[2,3-<7]-l,3-oxazin-4-one 178 (Equation 67). Treatment of this compound with hydrazine hydrate afforded the 3-amino derivative 179a while reaction with 4-methoxyaniline produced 179b <2000IJB764>. [Pg.369]

The preparation of a chiral bicyclic hydrazine, (15,35,5S)-2-amino-3-methoxymethyl-2-azabi-cyclo[3.3.0]octane (SAMBO, 3), was reported32 in 1990. (12 S, 31 S,51 5 )-2-Azabicyclo[3.3.0]-octane-3-carboxylic acid was resolved into its enantiomers. The (lS ,35,55)-enantiomer was converted to the chiral hydrazine 3 in six steps, utilizing Hofmann degradation, which is also employed in the preparation of SAMP. [Pg.995]

The majority of transformations carried out at ring substituents of bicyclic azetidinones were described in Section 5.12.3.3.2 for azetidinones related to cephalosporins and penicillins. Nucleophilic displacement reactions of 7-halo-l-azabicyclo[4.2.0]octan-8-ones with thallium phthalimide and hydrazine have been reported (76ACS(B)318). [Pg.358]

The 2-acetyl derivative of benzofuranone (93 R1 = Me) on treatment with hydrazine did not give the expected bicyclic system 94... [Pg.205]

For example, treatment of esters 819-21 with hydrazine in refluxing ethanol gave the N-unsubstituted bicycles 9 (R1 = H). 1-Methyl derivatives (9 R1 = Me) were also prepared.22 The hydrazine 11, obtained from the acid 10a, was heated at reflux without puriiication in dilute acid to give 12 (R = H). The acid chloride 10b furnished hydrazide intermediates 10c,17,23,24 which were cyclized by fusing the solid,23 refluxing with pyridine in the presence of copper powder,24 or by heating with potassium carbonate in 1-pentanol.17... [Pg.347]

Treatment of 3-acetylpyridines (140, R = H, Et) with hydrazine in refluxing glacial acetic acid produced the N-unsubstituted bicycles.132 1-Phenyl derivatives 141 (R = H, Me, Ph), however, were provided from acid-catalyzed cyclization of the corresponding hydrazones.133,134... [Pg.371]

Several amino compounds (170 R1 = H, Me R2 = H,CH2Ph) were obtained from analogous reactions in which the 3-cyano-4-aminotetrahy-dropyridines (169) were treated with hydrazines.153 Cyclization of the enols 171, however, under similar conditions afforded the tetrahydro bicycles 172 (R = H, Me).154,15 5... [Pg.377]

Two mechanisms (i.e. direct hydrolysis and alternatively a path via an unstable acyl phosphate intermediate) are involved in the hydrolysis in phosphate buffer of N-arylsulfonyl / -lactams such as (130).107 The acyl phosphate intermediate can be trapped with hydrazine. The alkaline hydrolysis of some torsionally distorted lactams, i.e. the bridged benz[rfe]isoquinolin-l-ones (131), in 70% (v/v) DMSO-water has been compared under the same conditions with the hydrolysis of AvA-dimethyl-1 -naphthamide (132). The relative rates of reaction and activation parameters indicate the effect of torsional distortion.108 The reaction of the tricyclic azetidinones (133) with trifluoroacetic acid gives the bicyclic thioesters (135). The mechanism may involve acid-catalysed elimination of methanethiol to give an azetinone intermediate (134) which, after nucleophilic attack of the thiol, is converted into (135).109... [Pg.56]


See other pages where Hydrazines bicyclic is mentioned: [Pg.299]    [Pg.299]    [Pg.281]    [Pg.92]    [Pg.125]    [Pg.245]    [Pg.168]    [Pg.170]    [Pg.333]    [Pg.406]    [Pg.309]    [Pg.359]    [Pg.703]    [Pg.325]    [Pg.339]    [Pg.68]    [Pg.20]    [Pg.1516]    [Pg.1518]    [Pg.223]    [Pg.783]    [Pg.87]    [Pg.90]    [Pg.111]    [Pg.550]    [Pg.162]    [Pg.66]    [Pg.14]    [Pg.681]   


SEARCH



Bicyclic hydrazine, asymmetric

© 2024 chempedia.info