Studies on the 1,2-Brook Rearrangement of Bissilyl Ketones

Abstract

The first 1,2-Brook rearrangements with bis(dimethyl-phenylsilyl) ketone, initiated after addition of different C- and S-nucleophiles, are described. The resulting, newly formed carbanion can be trapped with electrophiles thus paving the way for utilizing bissilyl ketones as formyl dianion equivalents in the future

[4+1] Cyclizations to Enantiopure Multifunctional Cyclopentanes from d-Glucose Using Formyl Dianion Synthons

“…However, the formation of formyl anions or dianions, a necessity for this approach, requires a temporary reversal (‘umpolung’) of the carbonyl reactivity. 3…”

“…7,7-Dithian-hexahydrocyclopenta[4,5]furo[2,3-d][1,3]dioxol-5-ol (13) The synthesis of 13 was carried out in an analogous fashion as described above for the preparation of cyclopentanol 12. The reagents [1,3]dithiane-2-yl-trimethylsilane 4b (1.35 ml, 7.30 mmol, 1.3 eq) and n-BuLi (2.5 M in hexane, 2.7 ml, 6.7 mmol, 1.2 eq) were reacted with epoxytosylate 9 (2.00 g, 5.61 mmol, 1.0 eq); after hydrolysis in the presence of TBAF (2.0 g, 6.45 mmol, 1.15 eq), dithiane 13 (1.30 g, 4.26 mmol 76 %) was obtained as a white solid material. m.p.= 112 °C; Rf = 0.20 (petroleum ether / ethyl acetate= 2:1); [a]D 20 = +24.0° (c = 1.0, CHCl3); 1 H-NMR (400 MHz, CDCl3, CHCl3= 7.26 ppm):  5.82 (d,J= 3.6 Hz,1 H,5.06 (d,J= 3.6 Hz,1 H,4.83 (dd,J= 5.3,4.7 Hz,1 H,4.39 (dddd,J= 10.6,10.5,6.1,4.7 Hz,1 H,3.16 (d,J= 5.3 Hz, 1 H, 5-H), 2.96-2.79 (m, 4H, dithiane), 2.52 (dd, J= 13.0, 6.1 Hz, 1 H, 2-H), 2.36 (d, J= 10.6 Hz, 1 H, OH), 2.12-1.95 (m, 2 H, dithiane), 1.85 (dd, J= 13.0, 10.5 Hz, 1 H, 2-H´), 1.53 (s, 3 H, acetonide), 1.37 (s, 3 H, acetonide) ppm; 13 C-NMR (100 MHz, CDCl3, CDCl3= 77.0 ppm);  112.3 (q, acetonide), 106.5 (t, C-7), 85.3 (t, C-6), 83.9 (t, C-4), 71.8 (t, C-3), 59.3 (t, C-5), 51.2 (q, C-1), 46,5 (s, C-2), 28.2 (s, dithiane), 28.0 (s, dithiane), 27.6 (p, acetonide), 27.0 (p, acetonide), 24.8 (s, dithiane) ppm; HRMS (ESI-LCT): calc.…”

“…[α]D 20 -50.0° (c 0.43, CHCl3); 1 H-NMR (400 MHz, CDCl3): δ 7.63 (dd, J = 5.7, 2.6 Hz, 1H), 6.21 (d, J = 5.7 Hz, 1H), 5.70 (d, J= 3.4 Hz, 1H), 5.48 (dd, J= 5.7, 2.6 Hz, 1H), 4.72 (d, J= 3.4 Hz, 1H), 3.16 (d,J= 5.7 Hz,1H), 1.56 (s, 3H), 1.36 (s, 3H) ppm; 13 C-NMR (100 MHz, CDCl3): δ 204. 3,161.3,135.1,113.2,106.6,82.4,81.4,54.8,27.9,27.0;HRMS calcd for C10H12O4: 196.0736; fragments found 181.0497 (M-CH3), 139,121,82,59.…”

“…However, the formation of formyl anions or dianions, a necessity for this approach, requires a temporary reversal ("Umpolung") of the carbonyl reactivity. 3 Recently, we reported a [4+1]-cyclization concept 4 that uses a silicon-mediated domino process leading to functionalized cyclopentanes 8. 4 The main features of this domino concept are a) chemoselective ring opening of the terminal oxirane in epoxytosylates 5 by a lithiated silyl-substituted methane derivative, followed by b) 1,4-Brook rearrangement with formation of a new organolithium species 7 and c) nucleophilic substitution of the tosyl group and ring formation to 8.…”

Development of Novel Photoinitiators as Substitutes of Camphorquinone for the LED Induced Polymerization of Methacrylates: A Bis‐Silyl Ketone

“…Albeit BSK has been already described in ref. [32] for other purposes in organic chemistry; its structure has never been used as photoinitiator of polymerization and the associated photochemical properties/photo chemical mechanisms were never reported. Moreover, BSK exhibits some similarity with the Ph 3 GeC(O)GePh 3 germyl ketone previously reported by us as a potential photoinitiator under visible light.…”