Cyclizations naphthoquinones with

Cyclization of 2-chloro-3-(A -benzoylhydrazino)-l,4-naphthoquinones with benzenesulfonyl chloride affords the... 

Benzocyclobutenedione 57 is transformed to the phthaloylmetal complex 58 by treatment with Fe(CO)5, RhCl(PPh3)3, and CoCl(PPh3)3. The phthaloyliron complex 58 (M=Fe) reacts with alkynes, and subsequent acidification under air then gives the naphthoquinone 59. The cyclization of the phthaloyl-cobalt 58 (M=Co) with alkynes requires AgBF4-activation [32]. (Scheme 22)... 

Condensations with hydrazine also yield pyridazines. For example, Shvartsberg and coworkers treated pen -acetylenic naphthoquinones 156 with hydrazine to give the six-membered pyridazine ring 158 after cyclization <00TL771>. 

Srinivasan found that the typical stoichiometric Pd(OAc)2 conditions effect cyclization of 2-(N-arylaminomethyl)indoles to aryl-fused p-carbolines in low yield [e.g., 51 to 52] [73]. Similar to the chemistry observed with N-(phenylsulfonyl)pyrrole, 1,4-naphthoquinone also undergoes Pd(OAc)2 oxidative coupling with A-(phenylsulfonyl)indole to give 53 in 68% yield [74],... 

A -Sulfonyl-2,2 -biindoles undergo a formal [4-I-2] cycloaddition with various dienophiles to produce indolocarba-zoles <2004TL4009>. Thus, reaction of 171 with A -benzylmaleimide in chlorobenzene in a sealed tube produces the cycloadduct in moderate yield (Equation 105) as the only observable product (Table 11). It is proposed that the reaction proceeds by an initial Michael addition, followed by a rapid cyclization and loss of the phenylsulfonyl group during the aromatization process. Similar cyclization reactions are observed with A -methylmaleimide, dimethylace-tylene dicarboxylate, and 1,4-naphthoquinone. 

The methylfuronaphthoquinone (33) has been obtained by reductive cyclization of the naphthoquinone (32) with zinc and hydrochloric acid and subsequent oxidation by chromic acid (74CJC88). Furans (35) have been prepared in excellent yields starting with the photochemical addition of an a-diketone to an alkylthioacetylene (34) followed by reductive... 

Regiospecific synthesis of naphthols.1 The o-allylbenzamide 1, obtained by directed o-metallation of tertiary amides (12,97-99, and previous references cited), on treatment with CH3Li (superior to LDA, sec-BuLi) cyclizes to the naphthol 2. This reaction provides an attractive route to naphthoquinones (equation I). 

Condensation of 5-(arylethynyl)-3-(diethylamino)naphthoquinones 64 with hydrazine afforded 3-benzyl-9-(diethyl-amino)bcnzo[zA ]cinnolin-7-oncs 66. Replacement of the arylethynyl substituent in the starting naphthaquinone by a 3-hydroxyalk-l-ynyl group leads to a change in the direction of cyclization, resulting in substituted naphtha[l,8-zv/ -l,2-diazepin-8-ones 65, as condensation products <2001RCB1668> (Scheme 13). 

As an oxidative addition-cyclization reaction, treatment of 1,4-naphthoquinone (128) and diethyl phenylmalonate (129) with Mn(OAc)3 in acetic acid generates benz[a]an-thraquinone (130) as shown in eq. 4.45 [125-132]. 

Chloro-3-(o -cyano-Q -carbethoxy)methyl-l,4-naphthoquinone 603 is cyclized by using Na2S to yield the corresponding thiophene 604 <1999JHC15>. Treatment of the 3-bromopropene 605 with NaSH affords tetrasubstituted thiophene 606 <2005SC2251>. 

A key step in the synthesis of the simple aromatic bisphenol tetrangulol (3) by Brown and Thomson [18] was a Michael-type cyclization of a phenol to the chloronaphthoquinone moiety (Scheme 3). The starting material 8, connecting the naphthoquinone and the protected phenol, was prepared by an interesting radical alkylation of the chloronaphthoquinone 6 with a carboxylic acid 7 in the presence of silver ions and persulfate with concomitant decarboxylation (Torsell reaction [19]) to yield the dihydrobenzo[a]anthraquinone 9. The synthesis of tetrangulol (3) was concluded by dehydrogenation in boiling nitrobenzene. 

The whole range of natural (2, 29, 155, 156) and also of the non-natural angucyclines 153 and 154 (not to mention their fully aromatized analogues) were now accessible by controlled aldol cyclization [86]. Our next goal will be the attachment of a C4 acetoacetic acid fragment onto the naphthoquinone core to arrive at partially cyclized precursors for biosynthetic studies similar to those performed with 4-deoxyaklanonic acid (133) [100]. 

Gordon and Danishefsky [112] used the reaction of a chromium Fischer car-bene complex 164 with a cycloalkine 163 to build the naphthoquinone core 165 (Dotz reaction, review [113]), a procedure often used for synthesis of the linearly condensed anthracyclinones (e.g., [114]). The quinone ketone 165 has nucleophilic and electrophilic centers correctly positioned to furnish a ben-zo[fl]anthraquinone. However, treatment with NaH or Triton B gave the spiro-compounds 166 as a mixture of two stereoisomers. These products evidently arose from Michael addition of the ketone enolate to the naphthoquinone double bond. But the weaker base DBU induced cyclization at ambient temperature to the benzo[a]anthraquinone 167 in 65% yield (Scheme 42). The primary aldol adduct apparently eliminated water and the resulting dihydrobenzo[a]anthraquinone aromatized under basic conditions in the presence of air. This is an instructive example of the influence of the base on the cyclization mode. 

AUylic bromination. [1, 79. after citation of ref. 8]. N-Bromosuccinimide reacts with isolapachol (I) in refluxing CCT by vinylic substitution to give (2) N-iodo-succinimide reacts in the same way.83 (8-1 sopropylfurano- 1,4-naphthoquinone (3) was obtained by cyclization of the vinylic bromide (2) with N1S and also by the action of two equivalents of N IS on (1). Even when the unsaturated side chain has a primary or secondary hydrogen in the allylic position, for example (4), the same vinylic substitution was observed (5). 

Af-Acyl-2-cyano-l-azadiene is sufficiently stable for its properties and reactions to be studied. It is a low-melting solid which reacts with the relatively weak dienophile norbomene in a Diels-Alder fashion [B-42] in boiling benzene over 7 h to give one main product and two minor stereoisomers of it [3853]. Similar reactions occur with the V. -dimethylhydrazone of 2-methylacrolein and 1,4-naphthoquinone or its pyridine analogue. In some of these cyclizations, there is good steroselectivity but in others, a mixture of positional isomers is formed [3279]. A Diels-Alder reaction of 2-azabuta-1,3-diene which carries the easily eliminated dimethylamino groups is a convenient route to an azacarboline [3108]. 

A series of dyestuffs has been prepared from l-alkyl-2,3-dimethylquin-oxalinium salts by reaction with 2,3-dichloro-l,4-naphthoquinone. The initial products of condensation such as 23 are cyclized to give naphthophenazinones (e.g., 24) in base but undergo acid-catalyzed cyclization to give pentacyclic derivatives such as 25." ... 

Naphthoquinone (122)62 63 64 on reductive acetylation afforded diacetate (123). Selective basic hydrolysis afforded monoacetate (124). This on benzylation followed by basic hydrolysis and alkylation with chloroacetone yielded compound (125). Its cyclization was attempted with tetrafluroboric acid in ether. The resulting compound (126) was immediately oxidized with selenium dioxide to Mansonone F (120). 

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