Annelated synthesis

Assereg, J.H., Glase, S.A., and Welch, S.C. 1987. 3-Chloro-2-[(diethoxyphosphoryl)oxy]-l-propene a new reagent for a one-pot cyclopentenone annelation. Synthesis of desoxyal-lethrolone, cw-jasmone, and methylenomycin B. Journal of Organic Chemistry, 52(8) 1440-50. 

Coumarins 3,4-annelated, synthesis and physiological activity of 82S337. Coumarins as active laser dyes 81YGK1200. 

The synthesis can be completed either by activating aldehyde (9) as an enamine and eliminating to give (10) before combining the two in a Robinson annelation (synthesis 2), or by the lazy man s method of simply using no control at all —with good results in this case (synthesis 3). 

If you don t see why the stereochemistry should be as 1 have drawn it, 1 suggest you make a model of 332A and discover for yourself There is a simple synthesis of 332A (X = OTs) from the Robinson annelation (frame 117) product 332B. 

The material in the succeeding chapters describes both the synthesis of the indole ring and means of substituent modification which are especially important in indole chemistry. The first seven chapters describe the preparation of indoles from benzenoid precursors. Chapter 8 describes preparation of indoles from pyrroles by annelation reactions. These syntheses can be categorized by using the concept of bond disconnection to specify the bond(s) formed in the synthesis. The categories are indicated by the number and identity of the bond(s) formed. This classification is given in Scheme 1.1. 

The synthesis of cyclohexenone derivatives by Michael addition followed by intramolec ular aldol condensation is called the Robinson annulation, after Sir Robert Robinson who popularized its use By annulatwn we mean the building of a ring onto some start mg molecule (The alternative spelling annelation is also often used)... 

Examination of the pyrazino[2,3-rf]pyrimidine structure of pteridines reveals two principal pathways for the synthesis of this ring system, namely fusion of a pyrazine ring to a pyrimidine derivative, and annelation of a pyrimidine ring to a suitably substituted pyrazine derivative (equation 76). Since pyrimidines are more easily accessible the former pathway is of major importance. Less important methods include degradations of more complex substances and ring transformations of structurally related bicyclic nitrogen heterocycles. 

Coumarin-3-carboxylic acid, 6-nitro-ethyl ester reduction, 3, 691 Coumarinic acid synthesis, 3, 685 Coumarinoisocoumarin synthesis, 3, 834 Coumarins acetoxylation, 3, 680 acylation, 3, 689 annelated... 

Cyclizations such as that which underlies the Knorr synthesis have also been successfully used in Robinson annelation sequences [72] (equation 12)... 

Reactions of 3- and 4-piperidone-derived enamines with a dienester gave intermediates which could be dehydrogenated to tetrahydroquinolines and tetrahydroisoquinolines (678). The methyl vinyl ketone annelation of pyrrolines was extended to an erythrinan synthesis (679). Perhydrophenan-threnones were obtained from 1-acetylcyclohexene and pyrrolidinocyclo-hexene (680) or alternatively from Birch reduction and cyclization of a 2-pyridyl ethyl ketone intermediate, which was formed by alkylation of an enamine with a 2-vinylpyridine (681). 

Amino-2,l,3-benzothiadiazole treated under similar conditions afforded, re-gioselectively, an analogous angularly annelated ester 68 and acid 69, both to be tested for inhibition of the DNA synthesis (74MI1). Subsequent alkylation of the... 

Skraup synthesis starting from 4- and 5-aminobenzothiadiazole afforded only angularly annelated products thiadiazolo[5,4-/i]- and [4,5-/]quinoline, respectively. Attempts to cyclize 4-chloro-5-aminobenzothiadiazole failed (37LA38). 

Annelation of chromium carbene complexes in synthesis of heterocycles 99CSR187. 

Inverse Diels-Alder reaction as synthetic tool in the synthesis of annelated heterocycles 95F419. 

Regioselective and stereoselective template synthesis in chemistry of fullerenes annelated with heterocycles or linked with heterocyclic fragments 99ACR537. 

Synthesis of [d]-annelated indoles by thermal electrocyclic reactions 95MI7. 

Synthesis of annelated furanoses and their transformation to carbocycles 98SL693. 

Synthesis, stereochemistry, and transformations of cyclopenta-, cyclohexa-, cyclohepta-, and cycloocta-annelated pyrimidines 98AHC(69)349. 

Synthesis, properties, and applications of nonsymmetric triazinones 99MI26. Transformations of 1,2,4-triazines by the action of C-nucleophiles 98ZOR327. 1,2,4-Triazine A -oxides and their annelated derivatives 98UK707. 

A. Synthesis of Annelated 1,2,4-Triazine 1-Oxides Involving a Nitro Group. 291... 

The Diels-Alder methodology can also be applied in the synthesis of tricyclic heterocycles, as was demonstrated by reactions of 2-(2-trimethylsilylethynylphenyl-X)pyrimidines (X = 0, S, NCOMe, CHj, CO). They are converted in good yield on heating at 160°C into tricyclic annelated pyridines (89T6511) (Scheme 37). A similar reaction was found with the 2-(2-allylphenoxy)pyrimidines affording azaxanthenes (79H665) (Scheme 37). 

Hydrogenolysis of methylenediisoxazoles have been useful in preparing substituted resorcinols and aminophenols (7). The isoxazole annelation reaction (71,89,90,91,103) is well suited to the synthesis of steroids and other complex molecules. 

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