A new method for the generation of isobenzofurans: A simple entry to substituted naphthalenes

Keay, Brian A.; Lee, D. K. W.; Rodrigo, R.

doi:10.1016/s0040-4039(00)78738-7

Cited by 20 publications

(8 citation statements)

References 11 publications

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“…Five‐membered hemiacetals are known to be very useful intermediates in various fields 11,14. Rodrigo et al14c reported the use of anthraquinone‐lactols in the syntheses of anthracyclinones. Rutledge et al14a as well as Rodrigo et al14c used similar lactols as starting materials for the syntheses of anthra[ c ]furans.…”

Section: Resultsmentioning

confidence: 99%

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Condensed Emodin Derivatives and Their Applicability for the Synthesis of a Fused Heterocyclic Hypericin Derivative

Waser

Falk

2006

Eur J Org Chem

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Investigations on the bifunctionalization of emodin at C(6) and C(7) with respect to the synthesis of a new class of fused heterocyclic hypericin derivatives were undertaken. The synthesis of such complex anthraquinone derivatives is possible by applying a Marschalk‐type reaction with emodin‐6‐carbaldehyde as the key step. The newly synthesized pyridazinone‐fused hypericin derivative possesses a satisfying bathochromically shifted absorption maximum making it a promising candidate for further investigations concerning a possible application in photodynamic therapy. Furthermore, the herein described strategy for the bifunctionalization of emodin provides a novel route for the synthesis of anthraquinone derivatives that are difficult to obtain by other methods.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

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Section: Resultsmentioning

confidence: 99%

“…Rodrigo et al14c reported the use of anthraquinone‐lactols in the syntheses of anthracyclinones. Rutledge et al14a as well as Rodrigo et al14c used similar lactols as starting materials for the syntheses of anthra[ c ]furans. However, these syntheses required rather harsh reaction conditions and are reported to proceed in low yields only.…”

Section: Resultsmentioning

confidence: 99%

Condensed Emodin Derivatives and Their Applicability for the Synthesis of a Fused Heterocyclic Hypericin Derivative

Waser

Falk

2006

Eur J Org Chem

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“…The same reaction applied to the closely related adduct 3 was a key transformation in our recent synthesis (2) of ( 2 ) daunomycinone. An examination of the process with a variety of oxabicyclo adducts' was conducted and the results (Table 1, Entries 1, 3, 6, 8, 1 1,13,16,18) confirmed the generality of the reaction. A reverse-Michael rationalization shown in Scheme 1 requires the development of some double bond character at a bridgehead and is also a 5-endo-trig reversal in violation of rules (3) formulated earlier and illustrated (4) with the furan 9.…”

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confidence: 84%

Anomalous 5-endo-trig reversals: general reactions of 7-oxabicyclo[2.2.1]heptenes and heptanes

Keay¹,

Rajapaksa²,

Rodrigo³

1984

Can. J. Chem.

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. 1093 (1984).Two general 5-endo-trig reversals of 7-oxabicyclo[2.2, llheptanes and heptenes are described and discussed. The reverseMichael reaction occurs with the aldehyde, ketone, ester, and nitrile derivatives while the reverse aldol reaction catalysed by acid is confined to the aldehydes and ketones. These properties of the title compounds are rationalized in terms of the geometric alignments of the bonding and antibonding orbitals of the bridging oxygen atom and its neighboring carbons. New isobenzofuran and cyclohexadiene syntheses form a part of the report. Early in our studies of the Diels-Alder reactions of isobenzofurans (1) we made the useful and intriguing discovery that adduct l a was smoothly converted to the dihydronaphthalene 2 a with methanolic sodium methoxide. The same reaction applied to the closely related adduct 3 was a key transformation in our recent synthesis (2) of ( 2 ) daunomycinone. An examination of the process with a variety of oxabicyclo adducts' was conducted and the results (Table 1, Entries 1, 3, 6, 8, 1 1,13,16,18) confirmed the generality of the reaction. A reverse-Michael rationalization shown in Scheme 1 requires the development of some double bond character at a bridgehead and is also a 5-endo-trig reversal in violation of rules (3) formulated earlier and illustrated (4) with the furan 9. No evidence could be obtained, however, to support any alternative mechanism; for example, no products of C(4)-0 cleavage were ever observed, thus excluding the possibility of a simple nucleophilic displacement at C ( l ) and(or) C(4). Deuteration at C(2) took place with esters and nitriles (entries 5, 7 , 10, 12, 15, and 17) and the deuterated products were endo-exo mixtures even when pure endo substrates ( l c and I d , entries 5 and 7) were used. Oxabicyclo ketones and aldehydes could not be deuterated cleanly with methanolic methoxide because of the rapid formation of products under the conditions. After 1 h at 20°C with this reagent, l a and l b , for example, were converted to a 1 : 1 mixture of products (2a and 2 b respectively) and deuterated starting materials. The lower acidity of the esters and nitriles must be responsible for rapid reprotonation of their enolates in methanolic methoxide, permitting clean deuteration in these cases and revealing the existence of a kinetic barrier to the reverse-Michael fission of the C(1)-0 bond. This behaviour is similar to the previously observed (4) deuteration of furan 9 and is interpreted similarly. Unlike the simple furan 9, however, which was inert to all bases, these compounds do suffer a forbidden 5-endo-trig cleavage with the strong base LDA under aprotic conditions (entries 6, 8, 1 1, 13, 16, and 18). Base-catalysed aromatizations observed in entries I Author to whom correspondence may be addressed. 'prepared by Diels-Alder reaction of furans and isobenzofurans with the appropriate dienophiles and used as endo-exo mixtures.2, 4, and 9 and previously with sodium acetate in refluxing methanol (5) must also occur through an initial ...

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“…The methylsulfonyl analog 7g was obtained by oxidizing the corresponding sulfide 7gg with m-chloroperbenzoic acid. The naphthalene 7e was prepared by reduction of the corresponding ester 6 9 with LAH. The preparation of the diol with a spacer methylene 7d was as follows.…”

Section: Chemistrymentioning

confidence: 99%

Novel Selective PDE IV Inhibitors as Antiasthmatic Agents. Synthesis and Biological Activities of a Series of 1-Aryl-2,3-bis(hydroxymethyl)naphthalene Lignans

et al. 1996

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A series of 1-aryl-2,3-bis(hydroxymethyl)naphthalene lignans have been synthesized and evaluated for their ability to selectively inhibit PDE IV isolated from guinea pig. Replacement of the 1-phenyl ring by a pyridone ring led to marked improvement of their selectivity for PDE IV over PDE III. The compounds that were most potent and selective involved those bearing an N-alkylpyridone ring at C-1. These compounds also showed potent antispasmogenic activity without causing significant changes in heart rate in the guinea pig. The most potent compound was 6,7-diethoxy-2,3-bis(hydroxymethyl)-1-[1-(2-methoxyethyl)-2-oxo-pyrid-4-yl]naphthalene (17f), ED50 values of histamine-induced and antigen-induced bronchoconstriction in the guinea pig being 0.08 and 2.3 mg/kg iv, respectively. This compound was chosen as a candidate for further pharmacological evaluation.

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A new method for the generation of isobenzofurans: A simple entry to substituted naphthalenes

Cited by 20 publications

References 11 publications

Condensed Emodin Derivatives and Their Applicability for the Synthesis of a Fused Heterocyclic Hypericin Derivative

Condensed Emodin Derivatives and Their Applicability for the Synthesis of a Fused Heterocyclic Hypericin Derivative

Anomalous 5-endo-trig reversals: general reactions of 7-oxabicyclo[2.2.1]heptenes and heptanes

Novel Selective PDE IV Inhibitors as Antiasthmatic Agents. Synthesis and Biological Activities of a Series of 1-Aryl-2,3-bis(hydroxymethyl)naphthalene Lignans

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