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Li-mediated treatment of phthalides with α-alkyl/arylacrylates provides a new, regiodefined approach to 2-substituted 1-naphthols.

The annulation of phthalides with α-alkyl/arylacrylates in the presence of LDA/LHMDS is shown to directly give alkyl/aryl-1-naphthols. The method involving a novel dealkoxycarbonylation obviates the regiochemical issues in the synthesis of polysubstituted naphthalenes, and it forms the key step in a three-step total synthesis of arnottin I, a naphthobenzopyranone natural product.

Ventinone A, a naturally occurring 1,4-dihydroxyanthraquinone has been synthesized in two steps from known compounds via a Hauser annulation. The same strategy, when applied to the synthesis of ventinone B, reveals that the proposed structure of ventinone B is identical with that of 4-methyl ether of erythroglaucin.

Hydrolytic decomposition of thiouronium salts A with aqueous NaHCO3 at 80° – 90 °C directly furnished thiolactones 6 -10 in very good yields in one-flask operation.

A Claisen rearrangement, the selective removal of a methoxycarbonyl group and an unusual oxidative cyclization are the key steps of the title syntheses.

Anionic cyclocondensation reaction of thiophthalides 1 with cyclohex-2-enones 2 followed by aromatization gives oxygenated hydroanthracenones 4 in good yields.

Hydrolytic decomposition of thiouronium salts A with aqueous NaHCO3 at 80° – 90 °C directly furnished thiolactones 6 -10 in very good yields in one-flask operation.

The reaction of thiophthalides 1 with aldehydes 3 in the presence of lithium tert-butoxide at –60 to 25 °C results in the stereospecific formation of only trans 2-(alk-1′-enyl)benzoic acids 4 in fairly good yields in one-pot operations. This reaction is proposed to proceed via episulfide formation followed by sulfur extrusion, and corroborated by an unprecedented reaction of phthalide with thiobenzophenone giving the acid 11a under similar conditions.

Glucose effects the Claisen rearrangement of allyloxy anthraquinones at low temperatures (100–130°C).

The anionic [4+2] cycloaddition ( 1→3 ) and the retro [4+2] cycloaddition ( 3→ 4 ) are coupled to evolve a general and high yielding three-step synthesis of 1,4-anthraquinones.

The synthesis and utility of unprecedented fluorenofurans 7 and oxa- s -indacenones 8 as key intermediates for synthesis of methoxsalen 1 is described, illustrating a novel synthetic approach to furocoumarins.

Annulation of indenone 5 with phthalide sulfone 6 has been successfully performed to furnish model benzo [b] fluorenone 7 , illustrating a potential route to kinamycin antibiotics.

The pentacyclic naphthoquinones 8 undergo unprecedented thermal rearrangement to cyclopent[a]anthraquinones 7 or 9 via a tandem Cope–cheletropic reaction path.

Anionic annulation of phthalide sulfones 3 with quinone monoketals 6 , accessible by phenyliodonium diacetate oxidation of naphthols 5 , offers a high yielding regiospecific entry to benz[ a ]anthraquinones 8 . Similar annulation of cyanophthalide 13 with 12 , followed by photooxygenation of 14 results in a complementary route to the basic skeleton 15 of nonaromatic A - ring angucyclines.

Department of Chemistry, Indian Institute of Technology, Kharagpur-721 302, West Bengal, India E-mail : dmal@chem.iitkgp.ernet.in Fax : 91-3222-255303 Manuscript received 31 December 2009, accepted 28 Jauuary 2010 Ventinone A, a naturally occurring 1,4-dihydroxyanthraquinone has been synthesized in two stepsfrom known compounds via a Hauser annulation. The same strategy, when applied to the synthesis or ventinone B, reveals that the proposed structure or ventinone B Is Identical with that of 4-methyl ether of erythroglaucin.

The crucial annulation of sulfone aldehyde 2 with enone 3 has led to an operationally simple two-step synthesis of benz[ f ]indene 1 , and its derivatives 8 and 9 involving a new rearrangement.

The sulfoxide esters 14 and 20d are successfully annulated with bicyclic enone 8 in the presence of t BuOLi to provide the pentacyclic ketones 9a and 21a respectively in good yields (≥70%). Flash vacuum pyrolysis of O-methyl derivatives 9b and 21b at ∼ 500° C/. 1 mm provide furoindacenones 16b and 22b respectively, which in turn are convertible to furocoumarins 1 and 3 .

The preparation and utility of a new polymer-anchored Pd II catalyst for the hydrogenation of a wide range of organic substrates is described.

Synthesis of brasiliquinones B and C, 2 and 3 and 3-deoxyrabelomycin 4a has been accomplished in 6–7 steps from the common precursor 18b. The key naphthalenones 6 were prepared in 5 steps from tetralone 17 in a regioselective manner. Anionic annulation of cyanophthalide 7c with 6 readily provided tetracyclic precursors 5 in excellent yields, sunlight-promoted photooxidation of which led to the synthesis of the title compounds.

Indenone epoxides 8 , prepared from the corresponding indenones, have been shown to undergo clean thermal rearrangement to give isocoumarins 10 in high yields. This synthesis of isocoumarins, when applied to oxaindacenone 7 , resulted in the total synthesis of coriandrin ( 1 ).

The first total synthesis of euplectin, a rare metabolite with a chromone annulated indenone motif, has been accomplished in 17 steps. This has been possible through interplay among three key reactions: a Hauser sulfoxide annulation, a new chromone formation and a late-stage retro-Diels−Alder reaction. The entire regiochemical integrity of the successful route is established by an iodine-catalyzed aromatization of a cyclohexane-1,3-dione and the Hauser annulation.

The bis-oxazoline-copper complex-catalyzed aziridination of alkenes followed by an intramolecular Friedel-Crafts alkylation of the tethered and in situ generated aziridine provides a one-pot, general and efficient method for the synthesis of trans-2-amino-1-aryltetralins from a mixture of 2-arylethylstyrenes (E/Z≤85:15) with excellent diastereo- (dr>99:1) and enantioselectivities (up to 92% ee).

DBU-CH3I has been poised to be a substitute for diazomethane in the preparation of methyl esters from carboxylic acids. The reactions can be carried out in commercial untreated acetone and acetonitrile, which have been exemplified with several methyl esters, otherwise it is difficult to prepare. Bis-esterification using diiodomethane can also be achieved in a similar fashion. Sufficiently acidic phenols are also conveniently O-methylated by the method.

The epoxyquinones (e.g., 24), readily assembled in one step from the quinols (e.g., 27) by a simplified version of the Dowd oxidation, are shown to undergo rearrangement to pyranonaphthoquinones (e.g., 28) and their ring contracted homologues (e.g., 29) on flash vacuum pyrolysis at 450 degrees C and 0.01 Torr. The rearrangement has been demonstrated to be useful for a regiospecific synthesis of lambertellin (3). Similarly, the masked aziridinocyclopentanone 9 rearranges to 2-pyridone (37).

In the title compounds, C 16 H 12 O 3 and C 17 H 16 O 3 , the six-membered ring of the norbornene moiety adopts a boat conformation and the five-membered rings formed by the methylene bridge adopt envelope conformations; the other rings in the molecules are nearly coplanar. In the solid state, both compounds exhibit O-H…O and C-H…O hydrogen bonds.

The title compound, C 19 H 14 O 4 , exists in the quinol form. The six-membered and five-membered rings of the norbornene moiety adopt boat and envelope conformations, respectively. The hydroxyl groups are involved in O-H…O intramolecular hydrogen bonds.

DBU catalyzed condensation of phthalaldehydic acids and 1,3-diketones has been developed to be a general method for the synthesis of 3-substituted phthalides. This method, in combination with mercuric acetate mediated oxidative aromatization has been utilized for the regiospecific synthesis of isopestacin (9) and cryphonectric acid (10).

3-Phenylsulfanylphthalides (e.g. 8a) readily react with p-benzoquinones in the presence of LiOtBu in THF to furnish 1,4-dihydroxyanthraquinones in good yields and one-pot operations.

1-8-Diazabicyclo[5.4.0]undec-7-ene(DBU)‐catalyzed Michael addition of nitroalkanes to dicyclopentadienone (1) followed by flash vacuum pyrolysis (FVP) provided a high‐yielding synthesis of extremely pure 4‐nitroalkyl cyclopentenones (3). The optimized Nef reaction of the nitro adducts (2) provided 4‐ketoalkyl cyclopentenones (5) in the similar way.

The six-membered ring of the title compound, C 15 H 17 NO 4 , adopts a half-chair conformation, and the methyl and nitro groups are attached equatorially to it. The five-membered ring fused to it is in a flattened envelope conformation. In the norbornene ring system, the six-membered ring adopts a fairly symmetrical boat conformation and the two five-membered rings formed by the bridging C atom adopt envelope conformations. The mean plane through the fused five-membered ring forms dihedral angles of 31.14(5) and 84.28 (7)° with the mean planes of the adjacent six-membered rings.

Suitably N-protected furoindolones react regioselectively with a variety of Michael acceptors in the presence of LDA to give 1-hydroxycarbazoles in a single-pot process and in good yields. The methodology has been applied to the synthesis of murrayafoline-A.

Using two different conditions for the BAIB [bis(acetoxyiodo)benzene] oxidation to tetrahydro‐β‐naphthols or substituted tetrahydro‐β‐naphthols furnished two different products with excellent yields.

The first synthesis of BE-23254, an unusual angucycline antibiotic, is reported. It involves regioselective condensation of naphthalenone 4 and chlorine-containing isobenzofuranone 16 as the key step.

Quinol ethers and quinone monoketals are shown to undergo formal anti-Michael addition reactions with allylindium reagents at room temperature to give only ortho allylated phenols in good yields.

A new methodology for the rapid regiospecific synthesis of benzonaphthopyranones has been developed, on the basis of a tactical extension of the Hauser–Kraus annulation. The prowess of the methodology has been illustrated by a short synthesis of chartarin ( 22b ) and a facile entry to the chrymutasin scaffold ( 26 ).

Hydroxybenzo[b]thiophene is an important benzo[b]thiophene derivative because of its role as an intermediate in the synthesis of condensed sulfur heterocycles. The hydroxyl group can be converted into O-carbamate and the latter utilized in the regiocontrolled introduction of substituents through directed metallation. In the present review, synthesis, properties and reactions of various hydroxybenzo[b]thiophenes are described.the pyranoxanthone (14) and its prenylated derivative (31) followed by a Claisen rearragement leading to the target substrate (7).

[reaction: see text] Condensation of the phthalide sulfide with an ortho-quinone monoketal was employed as a key step in the first total synthesis of a derivative of (+/-)-PD 116740.

Department of Chemistry, Indian Institute of Technology, Kharagpur-721 302, India Manuscript received 27 July 1999 Furan-1,4-dipolar agents 7 and 16e, prepared in few steps from commercially available furoates, have been annotated with bicyclopentadienone 2 to provide pentacyclic frameworks 8 and 17 respectively. Subsequent transformations of 8 and 17 through retro-Diels-Aider reaction and indenol-indanone rearrangement have furnished psoralen precursors 14 and 19. Similarly, oxaindacenone 23 has been prepared in good yield from 21.

Vinyl cyclopropanes are an important class of monomers which on radical ring opening polymerization (RROP) lead to polymers having cyclic moieties, carbon-carbon unsaturation and different other functional groups inside its backbone as in the pendant group. This investigation reports controlled radical ring opening polymerization (CRROP) of 1,1-bis (ethoxy carbonyl)-2-vinylcyclopropane (BCVCP) catalyzed by Cu catalyst. In this case homo and co-polymerization of BCVCP was carried out via ATRP using ethyl-2-bromoisobutyrate as initiator and CuBr as catalyst in combination with Me6-TREN ligand. Radical polymerization of BCVCP and its copolymerization with methyl methacrylate (MMA) via ATRP led to predominantly 1,5 ring opening polymerization leading to linear polymers with >CC< in the main chain of the polymer. Conventional free radical co-polymerization of BCVCP and MMA led to polymers predominantly with cyclic rings in the main chain. The polymers were characterized by NMR, FT-IR, GPC, DSC and TGA analysis.

In the title compound, 2-bromo-5,5-di­methoxy­benzo­[a]­anthracene-6,7,12(5H)­trione, C20H13BrO5, the two aromatic rings are essentially planar and make a dihedral angle of 15.1 (2)° with one another, while the di­methoxy-substituted cyclo­hexane ring is non-planar, as expected. An intramolecular C—H⋯O interaction is present, with C⋯O = 2.814 (5) A and C—H⋯O = 125°.