Synthesis and Properties of 4,4,9,9‐Tetramethyl‐1‐oxa‐cycloundecane‐5,6,7,8‐tetrone and 5,5,10,10‐Tetramethyl‐1‐oxa‐cyclotridecane‐6,7,8,9‐tetrone

Abstract

The synthesis of 4,4,9,9-tetramethyl -1 -oxa-cycloundecane -5,6,7,8tetrone (9) and 5,5,10,1O-tetramethyll-oxa-cyclotridecane-6,7,8,9-tetrone (10) has been achieved in a multistep procedure. The key steps in this synthesis were the ring closure of 23 and 24 to 25 and 26, respectively, and the oxidation of the triple bond with RuO,/NaIO, to the dihydroxydiketones 31 and 32. Compound 9 is the first cyclic tetraketone for which an intramolecular donor-acceptor stabilization has been found. A strong transannu-In this paper we report a new reaction pathway that overcomes the above-mentioned limitations. We report the synthesis of 4,4,9,9-tetramethyloxacycloundecane-5,6,7,8-tetrone (9) and its congener 5,5,30,3O-tetramethyloxacyclotridecane-6,7,8,9tetrone (10). I0 Results and DiscussionSynthesis: We started our synthesis with the diols 11 and 12, prepared by conventional methods as described recently.['OIThe diols were treated with one mole of triisopropylsilyl trifluoromethanesulfonate (TIPS triflate)" 'I in a dilute solution to give the monoprotected alcohols 13 and 14, respectively (Scheme 2). The oxidation of the alcohol function with pyridinium chlorochromate (PCC)['21 gave the corresponding monoaldehydes 15 and 16 in good yields. A C, unit was introduced by reaction of 15 and 16 with the dilithium salt of acetylene (Li,C,) to yield the ynols 17 and 18, respectively. Protection of the secondary alcohol group with dihydropyran (DHP)" 31 in pres-

The solid state conformation of oxo stabilised ylides: X-ray structures of four new polyoxo phosphorus ylides

“…The same method predicted two angles of 127Њ for triones and either 180Њ, 90Њ and 180Њ or 3 × 130Њ for tetraones. 66 Even in the cyclic tetraones 80 67 and 81 68 the adjacent carbonyl groups are at intermediate angles to one another.…”

The Chemistry of Vicinal Polycarbonyl Compounds

“…The free tetrones were obtained directly. The oxacyclic compounds 85 84 and 86 85 and the dioxacyclic compound 82b 86 were prepared via the acetylenic aldehyde procedure.…”

“…Four X-ray structures of tetraketones have been reported (see Charts 1 and 2) to date: diphenyl tetraketone (2a), 164 dimesityl tetraketone (2c), 165 4,4,9,9-tetramethyl [12]paracyclophane-5,6,7,8-tetrone (84), 83 and 4,4,9,9-tetramethyl-1-oxacycloundecane-5,6,7,8-tetrone (85). 84 The most relevant structural data are listed in Table 3. As with vicinal triketones, we compare the torsion angles between the CO groups (R 1 -R 3 ) and the C-C and C-O bond lengths within the tetraketone unit.…”

“…The UV-vis spectra of open chain vic-tetraketones were reported many years ago by Horner and Maurer 193 and are summarized in the earlier review. What is new are data from cyclic tetraketones such as the cyclododecatetrone 81, 81 the cyclotetradecatetrones 82a 81 and 82b and the [12]paracyclophanetetrone 84, 83 the cyclic oxoundecanetetrone 85, 84 the cyclic oxotridecanetetrone 86. 85 With the exception of 82b and 85, all show a long-wavelength band between 507 and 533 nm with low extinction typical for a π* r n transition.…”

A Cyclic Vicinal Bis(tetraketone) and Structural Investigations of Formoins

“…[5] of a butane-2,3-dione fragment 1, [6,7] or of a 1,4-diprotected 1,4-dihydroxy-2-butyne moiety 4. [8] The last two possibilities are shown schematically in Scheme 1.…”