Tricyclic ester

R = H, R =Br, R" =Et) was prepared by cyclization of aroylacetate 314 (R = H, R =Br, r2 = H, X = F) (OOMIPIO). 9,10-Difluoro-3(5)-methyl-7-oxo-7//-pyrido[l,2,3- /e]-l,4-benzoxazine-6-carboxylic acid and its racemic form were prepared in the reaction of ethyl 2-(2,3,4,5-tetrafluorobenzoyl)-2-ethoxymethyleneacetate and (R)- or (i ,5)-2-aminopropanol and subsequent hydrolysis of the ring closed tricyclic esters (98MI45). Cyclization of ethyl 2-(2,3-difluoro-5-iodobenzoyl)-2-[A-(2-hydroxyethyl)aminomethylene]acetate 315 in the presence of K2CO3 in DMF at 95 °C for 3.5 h yielded 9-iodo-7-oxo-2,3-dihydro-7//-pyrido[l,2,3- /e]-l,4-benzoxazine-6-carboxylate (01MIP2). 

Winkler and Kwak144 recently prepared tricyclic ester 221 from 215 by means of three consecutive Diels-Alder reactions with 216, 218 and 91b to give 217, 219 and 220, respectively, followed by cleavage of the triple adduct 221 from the resin (equation 61). The overall yield was almost three times higher than when the same reaction sequence was performed in solution, thereby demonstrating the efficiency of resin-bound reactions in this case. 

With lithium (S)-methoxymethylpyrrolidinide as a base, the tricyclic esters 231 a and 231 e were obtained in 32 and 85 % yield with an enantiomeric excess of 30 and22%,respectively [104b]. 

Cycloalkadienolates with other than six-membered ring sizes reacted with the chloro ester 1-Me in the same manner (Scheme 69) [104b, 107], and the yields of the resulting unsubstituted tricyclic esters 243a,b were even better than that of 231a from the unsubstituted cyclohexadienolate [107]. 

The electron-deficient C —C double bond of dimethyl trieyclo[4.2.1.02S]nona-3,7-diene-3,4-dicarboxylate readily reacted with 2-diazopropane to give the [3 + 2] cycloadduct dimethyl 6,6-dimethyl-4,5-diazatricyclo[7.2.1,02 8]dodeca-4,10-diene-3,7-dicarboxylate (21b) by attack at the a-face.27 Similar reaction of the tricyclic ester with diazomethane gave dimethyl 4,5-di-azatricyclo[7.2.1.02-8]dodeca-4,10-diene-3,7-dicarboxylate (21a).28... 

The same cascade reaction of the iodo-triene (296) with Bu3SnH produces tricyclic esters (297a) and (297b) via triple 5-exo-trig ring closure as shown in eq. 3.123. 

Psychotrine (6) has already been synthesized by condensation of the (—)-tricyclic ester 29 with 3-benzyloxy-4-methoxyphenethylamine, followed by Bischler-Napieralski cyclization and debenzylation (76). Thus, the syntheses of (—)-29 reviewed last in Section III,B constitute formal syntheses of this alkaloid. 

The originally proposed gross structure 94 for (-l-)-alangicine (93) has now been revised to the complete expression 9 as a result of the syntheses of ( )-9 and (+)-9 by Fujii et al. (96,97). Alkaline hydrolysis of the ( )-tricyclic ester 49, the racemic ankorine precursor (42), furnished the ( )-amino acid 95... 

The tricyclic esters 439 were converted to the tetracyclic compounds by treatment with trimethylsulfoxonium iodide in dimethyl sulfoxide in the presence of sodium hydride... 

The quinazolinones 485 were cyclized to the tricyclic esters 486 by reaction with sodium ethoxide in ethanol at ambient temperature. When the tricyclic esters 486 were hydrolyzed with potassium hydroxide and subsequently acidified, decarboxylation took place spontaneously to give 487. 

A new synthetic approach to ( )-protoemetine [( )-6] was reported by Brown and Jones (68), who prepared the tricyclic ester ( )-77 from the cyclopentenolone ( )-78 through the lactol ( )-79 and the tetrahydronico-... 

Anionic oxy-Cope intermediate 36, derived from a-tetralone in several steps, undergoes rapid rearrangement to (E)-31. which gives the tricyclic ester 38 in a transannular reaction on treatment with 1% sodium ethoxide in ethanol936. 

Keese and coworkers have also used the intermolecular arene-alkene photocycloaddition reaction as a key step in another route to [5.5.5.5]fenestranes. Irradiation of 84 gave a mixture of products from which the desired adduct 85 could be isolated. Structure and stereochemistry of this tricyclic ester are supported both by earlier experience with the... 

PGF a methyl ester reacted with thallium (III) acetate in acetic acid to give the enol ether (79) which reacted further to give the tricyclic esters (80) and (81)". ... 

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