2- 2,3-dihydrobenzo furan

Chlorine or bromine add across the C=C bond of the furan ring, giving 2,3-dihalo-2,3-dihydrobenzo[/)]furans. Base-promoted dehydro-... 

These methods utilize molecules of type B (p. 362) (=104) a. Synthesis of Benzofurans by Thermal Ring Closure and Cyclodehydrogenation (Thermal, Catalytic or Photochemical) of o-Substituted Phenols. The Hansch Reaction. o-Alkylhydroxy-compounds on heating with a suitable catalyst give either a benzofuran or a 2,3-dihydrobenzo-furan with the same number of carbon atoms.285-292 Side products are formed by decomposition of the starting material. The initial phenol can be o-alkylated and ring-closed in one stage. 

Iodomethyl-2,3-dihydrobenzofurans (196) and the corresponding 2-iodomercurimethyl derivatives can be obtained from o-allylphenols and mercuric acetate, via the 2-acetoxymercuri-2,3-dihydrobenzo-furans.420... 

The same intermediate occurs in the Lehmann method463 for converting the methiodides of phenolic Mannich bases into 2,3-dihydrobenzo-furans, through reaction with dimethyloxosulfonium methylide. Thus, o-benzoquinone methide (207) leads to 2,3-dihydrobenzofuran according to Scheme 4. Similarly, 2-naphtholgives l,2-dihydronaphtho[2,l-6]furan through 208 and 209, formed and rearranged in situ.i6i The reaction has been applied to the synthesis of polycyclic benzofurans.483,485... 

Pd/C in AcOH515 539 or on Pd/BaS04 in AcOH,534 the reaction proceeds through to the 2,3-dihydrobenzofuran stage. Some catalysts (Raney nickel at 60° 50 kg/cm2) lead directly from 237 to 2,3-dihydrobenzo-furan derivatives, without going through the acetoxy derivatives.516 The corresponding benzofuran derivative is obtained under normal pressure.516... 

Dinitro-6-phenyliodonium phenolate (146) is a stable iodonium zwitterion484. It reacts under photolytic conditions with various alkenes, alkynes and aromatic compounds to afford 2,3-dihydrobenzo[ ]furans, benzo[6]furans and 6-aryl-2,4-dinitrophenols. The mechanism involves hypervalent iodine compounds (iodinanes, 147) and is illustrated for the reaction with an aromatic compound (equation 127). Compounds 148 are the major products when ArH = PhH, PhOCH3 or 1,4-dimethoxybenzene. With furan and thiophene, 149 is the principal product. The reaction does not proceed with chlorobenzene and nitrobenzene. 

Dihydrobenzo[ furan is reductively cleaved by treatment with hydrosilanes in the presence of catalytic amounts ofB(G6Fs)3 in high yield giving 2-phenylethanol <2000JOC6179>. l,3-Dihydrobenzo[c]furan is cleaved to the lithium alkoxide of 2-hydroxymethylphenylmethyllithium, which can be usefully trapped with electrophiles <2004S1115>. 

Indeed, the tandem sequence based on lithiation-cyclization followed by trapping of the lithiated cyclic intermediate 277 by appropriate electrophiles afforded good to excellent yields of alkyl substituted 2,3-dihydrobenzo[ >]furanes 278 (Scheme 85). 

As depicted in Equation (68), anodic fluorination of ethyl 3-benzo[4]furanyl acetate was applied to the synthesis of a 2,3-difluoro-2,3-dihydrobenzo[/ ]furan derivative. A 2-fluoro-3-hydroxyl derivative was also obtained as a minor product <2003SL1631>. 

Substituted-2-phenylbenzo[. ]furans were able to undergo a palladium-catalyzed hydrogenation reaction to give their corresponding 2,3-dihydrobenzo[ ]furans, but the yields are quite low (Scheme 51) <2002T4261>. 

The chemistry of 2,3-dihydrobenzo[ ]furan 257 discussed herein is focused on the furan part, rather than on the phenyl part, where its chemistry is similar to that of benzenoid molecules. For the chemistry based on the furan part, the frequent reports are related to the C-O bond cleavage. For example, by using an electron-rich ligand-based PCys/ Ni(acac)2 as a catalyst, 2,3-dihydrobenzo[ ]furan 257 was employed to couple aryl groups to afford biaryl compounds, as can be seen in Equation (150) <2004AGE2428>. 

As shown in Equation (151), in the presence of a catalytic amount of BF3, 2,3-dihydrobenzo[ ]furan 257 was converted to its corresponding phenol iodide by treatment with SiCU/Lil <2004TL3729>. o-2-Bromoethylphenol... 

Flavones have been shown to suffer from a stereospecific ring contraction to give rra r-2-aryl-2,3-dihydrobenzo[ ]-furan-3-carboxylates upon treatment with phenyliodonium acetate, trimethyl orthoformate, and sulfuric acid (Equation 151) <2002T4261>. 

DRL100 CAS 50539-74-7 HR 3 2,2-DIMETHYL-2,3-DIHYDROBENZO-FURAN-7-YL-N-(4-BROMOPHENYL-THIO)-N-METHYLCARBAMATE... 

Isopropylation of toluene by isopropyl halo- and alkyl-sulfonates (equation 54) has been performed by Olah et al. A variety of cattdysts, such as AlCb, AlCb-MeNOa and Nafion-H were employed, and the isomer distribution (o, m, p) in the product was determined. Sartori et al have recently reported an unusual Friedel-Crafts alkylation of lithium phenolates with ethyl pyruvate in the presence of AlCb to afford a-(2-hydroxyphenyl)ethyl lactates (22), which are the precursors of 3-methyl-2,3-dihydrobenzo-furan-3-ols (23 Scheme 6). 

A number of 2,3-dihydrobenzo[ ]furans can be made by the Ru-catalyzed olefin-metathesis approach in the presence of trimethylsilyl vinyl ether <04AG(E)4063>. The isovanillin derived benzofi ]furan was also made by the olefin metathesis approach <04H(63)I771>. 

Thehydroxybenzofuranderivative,5-hydroxy-2-oxo-3-phenyl-2,3-dihydrobenzo-furan underwent 2-alkylation and ring closure with 4-(2-n-butoxyethoxy)mandelic acid in acetic acid at 110°C containing sulphuric acid during 9 hours, followed by oxidation by the addition of ammonium persulphate with further reaction at 110°Cfor 1 hour (ref.72). 

Products formed include the cis- and trans-isovaers of 2-trinitromethyl-3-nitro-2,3-dihydrobenzofuran, 2-trinitromethyl-3-hydroxy-2,3-dihydrobenzofuran (from hydrolysis of the nitrite ester), 2-nitro-3-trinitromethyl-2,3-dihydrobenzo-furan, 4-trinitromethyl-7-nitro-4,7-dihydrobenzofuran and nitronic ester (274). ... 

A strategy for the catalytic diarylation of alkenes involved the migratory insertion of alkenes into an Ar-Cu complex to generate a new C(sp )-Cu complex, which subsequently underwent reaction with an aryl iodide to facilitate vicinal diarylation of an alkene. The method provided access to 2,3-dihydrobenzo[ ]furan-containing products (14JA14730). 

A soln. of 2-(2-bromophenoxy)ethyl chloride in THF containing a little 1,2-dibromo-ethane added to Mg and THF, the mixture heated to 60°, cooled to 30°, treated dropwise over 1.5 h with further stock soln., and refluxed for 2 h - 2,3-dihydrobenzo-furan. Y 76%. Use of -BuLi resulted in partial butylation. F.e.s. R.J. Alabaster et al.. Synthesis 1988, 950-2. 

Jimenez-Gonzalez, L., Garcia-Munoz, S., Alvarez-Corral, M., Munoz-Dorado, M. and Rodriguez-Garcia, I. 2006. Silver-catalyzed asymmetric synthesis of 2,3-dihydrobenzo-furans A new chiral synthesis of pterocarpans. Ghem. Eur. J. 12 8762-8769. 

Interpretation of the MS of a hydrolytic product (59), however, was exempt from such difficulties. The stereochemistry of the 7,8-bond in 8.1a was established upon comparing ORD curves of the hydrogenolysis product fiO and appropriate 2,3-tra j -2-aryl-3-methyl-2,3-dihydrobenzo-furans of known absolute configuration. 

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