Synthesis of Functionalized Cycloprop[f]indenes via the Carbene Addition Route

Abstract

The synthesis of4,5-dihydro-1H,3H-cycloprop[flinden-4-ol (I) and diethyl4,S-dihydro-1 H,3H-cycloprop[flindene-4,4-dicarboxylate (26) starting from dime 4 is described. The cyclopentene ring is constructed by condensation of diethyl malonate to the dibromide 21. The key-step in the synthesis of 1 consists in a twofold Curtius degradation of 22, with subsequent reduction of the carbonyl group and aromatization. The skeleton of the isomer 31 is synthesized via cycloaddition of butadiene to cyclopent-4-ene-l,3-dione (7) and addition of dichlorocarbene to the adduct 27 after ketalisation. The attempted synthesis of dihydrocycloprop[flindene (2) by base-induced elimination of several appropriately substituted precursors failed.HELVETICA CHIMICA ACTA ~-Vol. 77 (1994) Scheme I 7 8 9 4-ene-1,3-dione (7). Addition of dichlorocarbene followed by functional-group modification and aromatization of the adduct 9 as above should lead directly to 2. Resultsand Discussion. ~ Synthesis of 4,s-Dihydro-I H,3H-cycloprop[ f/inden-4-01(1) j r o m 4. The double Curtius degradation of geminal diesters, which is the key step in the proposed synthesis of 1, has been used only once in the literature [6]. Model studies were carried out in order to establish the feasibility of the approach in our system. 1,2-Bis(bromomethy1)benzene (10) was condensed with diethyl malonate [7] to afford 11, which was hydrolyzed [8] to the diacid 12 (Scheme 2). Reaction of 12 with oxalyl chloride afforded the dichloride 13, and treatment of the latter with NaN, in MeCN at 25" led to the azide 14. The azide was rearranged to the bis-isocyanate 15 by refluxing in cyclohexane. Hydrolysis of the crude 15 afforded indan-2-one (16) in 45-50% overall yield. 10 11 X = EtO 12 X = O H 13 X=C1 14 X = N , 15 X = NCO 16 X,X = 0

Syn-Dihydroxylation of Alkenes Using a Sterically Demanding Cyclic Diacyl Peroxide

“…Urea hydrogen peroxide (0.76 g, 8.05 mmol) was added to methanesulfonic acid (2.33 mL) and stirred in a water bath for 3 min. Indane-2,2-dicarboxylic acid 29 (0.56 g, 2.7 mmol) was added to the solution, and the reaction was stirred for 24 h in a water bath. 14a A mixture of ice/ethyl acetate (7 g/8 mL) was added to the reaction mixture and stirred for 5 min.…”