ChemInform Abstract: STRUCTURAL STUDIES OF 1,8‐DISUBSTITUTED NAPHTHALENES AS PROBES FOR NUCLEOPHILE‐ELECTROPHILE INTERACTIONS

Schweizer, W. B.; Procter, Garry; Kaftory, Menahem; Dunitz, J. D.

doi:10.1002/chin.197915084

Cited by 2 publications

(4 citation statements)

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“…and C0,Et groups is 2.665 P\ whereas the corresponding distances in compound (5) are 3.363 and 3.1 50 A. The results demonstrate the existence of an attractive nucleophile-electrophile interaction in (4).…”

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confidence: 74%

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Conformations of derivatives of 3,7-diazabicyclo[3.3.1]nonan-9-one. Comparison of 3-ethoxycarbonyl-7-methyl-1,5-diphenyl-3,7-diazabicyclo[3.3.1]nonan-9-one and 3,7-di(ethoxycarbonyl)-1,5-diphenyl-3,7-diazabicyclo[3.3.1]nonan-9-one: effect of a nucleophile ? electrophile interaction on molecular geometry

McCabe¹,

Milne²,

Sim³

1989

J. Chem. Soc., Perkin Trans. 2

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confidence: 74%

“…carbonyl C, at the other. 4 The compounds (7) do not suffer the usual repulsive interactions that characterise other 1,8disubstituted naphthalenes and their N C distances of ca.…”

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confidence: 99%

Conformations of derivatives of 3,7-diazabicyclo[3.3.1]nonan-9-one. Comparison of 3-ethoxycarbonyl-7-methyl-1,5-diphenyl-3,7-diazabicyclo[3.3.1]nonan-9-one and 3,7-di(ethoxycarbonyl)-1,5-diphenyl-3,7-diazabicyclo[3.3.1]nonan-9-one: effect of a nucleophile ? electrophile interaction on molecular geometry

McCabe¹,

Milne²,

Sim³

1989

J. Chem. Soc., Perkin Trans. 2

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“…Next, reactions of the trans-epoxides with lithium dimethylcuprate were examined. It was found that, whereas treatment of the acetoxy epoxide (24) with an excess of lithium dimethylcuprate gave a complex mixture of products, the correponding benzyl ether epoxide (29) reacted cleanly and gave the expected alcohol (37) in good yield (85%). The benzoyloxy epoxide (26) was intermediate in behaviour, the alcohol (38) being isolated in 44% yield, and the p-methoxybenzoyloxy epoxide (27) was slightly better giving 55% of chromatographed alcohol (39).…”

Section: Rzo -1\1mentioning

confidence: 99%

“…The major epoxide in each case was identified as the trans-epoxide, i.e. (24)- (29). This stereoselectivity was predicted assuming the conformation shown in structure A,* 9' ' the axial allylic alkoxycarbonyl substi tuent providing more steric hindrance to epoxidation than the equatorial allylic methyl substituent ; the epoxidation of 4-acetoxy-2,6,6-trimethylcyclohexene (36) provides an analogy.…”

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confidence: 94%

A fragmentation approach to a maytansine synthon: lithium dimethylcuprate-opening of substituted cyclohexene epoxides. X-Ray structure determination of ethyl t-2,3-epoxy-c-6-p-methoxybenzoyloxy-1-methylcyclohexane-r-1-carboxylate

Sirat

Thomas

Wallis

1982

J. Chem. Soc., Perkin Trans. 1

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A scheme for the synthesis of maytansine synthons (3) is proposed. As background to this work, the stereoselective synthesis of several cyclohexene epoxides and their reactions with lithium dimethylcuprate are described. The sterically hindered cyclohexadiene monoepoxide (1 0) and the hydroxycyclohexene epoxide (1 3) were unreactive towards the cuprate reagent. However, epoxidation of the c-6-hydroxy-Imethylcyclohex-2-ene-r-I -carboxylate derivatives (1 8)- (23) gave, selectively, the trans-epoxides (24)-(29) which reacted regioselectively with lithium dimethylcuprate to give the alcohols (37)-(39). Epoxidations of the c-6-acyloxy-t-2-hydroxy-I -methylcyclohex-3-ene-r-l -carboxylates (44)-(46) were not stereoselective, whereas methyl c-6-benzyloxy-c-4-methoxy-I -methylcyclohex-2-ene-r-lcarboxylate (55) gave the trans-epoxide (56) which was converted into the alcohol (57) on treatment with lithium dimethylcuprate. Sodium borohydride reduction of the ketone (58) gave the cis-alcohol (59) which, on epoxidation and treatment with lithium dimethylcuprate, gave the lactone (61 ).The structure of the major epoxide (28) obtained on epoxidation of ethyl c-6-p-methoxybenzoyloxy-Imethylcyclohex-2-ene-r-I -carboxylate (22) was confirmed by an X-ray structure determination.Recently several elegant approaches to the synthesis of maytansine (l), and maytansinoids, have been described.' We were interested in developing a maytansine synthesis in which the key step was a Wharton fragmentation of a cyclohexyl toluene-p-sulphonate such as compound (2) to generate the synthon (3) which has several features of the ' western zone ' of maytansine. In particular, the stereochemistry of the fragmentation precursor (2) should ensure that the C(4)-C(5) doublebond is formed with the correct geometry, and that the chiral centres at C(6) and C(7) have the desired configuration. Moreover the C(9) carbonyl group is introduced during the fragmentation step. As a development of this approach, the introduction of the chiral centres at C(3) and C(10) stereoselectively into the fragmentation precursor was envisaged. We here describe attempts to synthesize polysubstituted cyclohexane derivatives related to the fragmentation precursor (2). Results and DiscussionThe ketone (4) was selected as the initial target. The first approach examined involved the introduction of the bulky C( 1)-C(3) side-chain onto a cyclohexadiene ring which was then functionalized using the bulkiness of the side-chain to control the stereochemistry.

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ChemInform Abstract: STRUCTURAL STUDIES OF 1,8‐DISUBSTITUTED NAPHTHALENES AS PROBES FOR NUCLEOPHILE‐ELECTROPHILE INTERACTIONS

Cited by 2 publications

References 1 publication

A fragmentation approach to a maytansine synthon: lithium dimethylcuprate-opening of substituted cyclohexene epoxides. X-Ray structure determination of ethyl t-2,3-epoxy-c-6-p-methoxybenzoyloxy-1-methylcyclohexane-r-1-carboxylate

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