Herstellung von (S)‐(2‐Methylbutyl)‐ und (S)‐(sek. Butyl)‐ketonen aus optisch aktivem 2‐Methylbutanol nach der Dithian‐Methode

Abstract

Die Abbildung zeigt das Anion rnit atomaren therrnischen Schwingungsellipsoiden und Bindungslangen [51. Die geschatzten Standardabweichungen betragen ca. 0,005 t% fur P-P und 0,010 A fur P-0. Damit weichen die beiden P-P-Abstande nicht signifikant von ihrem Mittelwert 2,237 t% ab, wenngleich der beobachtete Unterschied sich rnit der annahernd gestaffelten Konformation (siehe Abbildung!) der kurzeren und der annahernd ekliptischen Konformation der langeren Bindung korrelieren IieDe. In (2) wurde fur den P-P-Bindungsabstand 2.20 + 0.05 t% (Mittelwert) gefunden. in (3) 2,170 . 0,003 A. Die relative Aufweitung in (I) hangt moglicherweise rnit der hoheren elektrischen Ladung des Anions zusammen [5/3 Elektronen pro P-Atom in (I) gegenuber 1 Elektron in (2) und ( 3 ) ] . Die P-0-Abstande sind im Rahmen der Genauigkeit alle

Synthetic applications of 2-chloro-1,3-dithiane. 2. Reactions with carbon nucleophiles

“…An analytical sample was prepared by crystallization from benzene-hexane as blue needles: mp 88.5-89. 1275 (PhNC), 905 cm"1; NMR (CDClg) 7.33 and 6.61 (AA'BB', 4 H, :V = 9.5 Hz, PhH), 5.10 (s, 1 , 2-H), 3.30 (q, 4 H, 3J = 7.0 Hz, NCH2), 2.8-2.95 (m, 4 H, 4, 6-H), 1.85-2.0 (m, 2 , 5-H), 1.12 2-[2'-(l',3'-Dithianyl)]thiophene (14). The crude product contained, besides 14 (~40%), considerable amounts of 9 and 12 [NMR (CDClg) 2-H in 9 and 12 4.92 (s), and formyl-H in 12 10.16 (s)].…”

Fixation of Heterocumulenes. 1. A Theoretical Study on the Irreversible Reaction of CO2 with a 2-Lithio-1,3-dithiane

“…The carbonyl group is converted into a cyclic thioacetal that, due to the carbanion stabilizing effect of the sulfur, can be easily deprotonated. These reagents can be employed in the synthesis of aldehydes, silyl and germanyl ketones, optically active aldehydes and ketones, cyclic carbonyl compounds, carbohydrates, and α-keto acids …”

Synthesis of (.+-.)-cacalol

“…

2-[2'-(l',3'-Dithianyl)]thiophene (14). The crude product contained, besides 14 (~40%), considerable amounts of 9 and 12 [NMR (CDClg) 2-H in 9 and 12 4.92 (s), and formyl-H in 12 10.16 (s)].1 Purification of 14 was achieved by careful column chromatography (G, benzene), followed by crystallization from hexane: white needles; mp 77-78 °C; IR 855, 760, 700 (thiophene), 905 cm-1.

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“…The reaction mixture was filtered and the filtrate evaporated to dryness leaving a pale yellow oil which was dissolved in hexane-benzene (1:1) and chromatographed on 90 g of Woelm silica gel. Elution with hexane-benzene (1:1) gave 0.23 g of recovered phenol, while the benzene fractions afforded 2.43 g (73% based on phenol consumed) of methyl ether 13 as a colorless oil: IR 5.99 pm; NMR 6-Acetoxy-5-methoxy-1,8-dimethyl-1,2,3,4-tetrahydronaphthalene (14). To a solution of 2.43 g of 6-acetyl-5-methoxy-l,8-dimethyl-1,2,3,4-tetrahydronaphthalene (13) in 180 mL of methylene chloride was added 4.10 g of m-chloroperoxybenzoic acid (80-90%) and 0.60 g of toluenesulfonic acid.…”

“…A. A solution of 1.247 g of 6-acetoxy-5-methoxy-1,8dimethyl-1,2,3,4-tetrahydronaphthalene (14) in 40 mL of methanol and 20 mL of 15% aqueous potassium hydroxide was heated at reflux under nitrogen for 2.5 h. After cooling, the reaction mixture was acidified with concentrated hydrochloric acid and extracted with two portions of ether. The combined ethereal extracts were washed with water and brine and dried, and the solvent was removed at reduced pressure to give 0.945 g (91%) of phenol 15 as an air-sensitive, palebrown oil, which was used immediately for the subsequent step: IR 2.88 µ ; NMR 1.10 (d. J = 7 Hz, 3 H, CHCHg), 2.20 (s, 3 H, ArCHg), 3.69 (s, 3 H OCHg), 5.41 (br s, 1 H, OH), 6.54 (s, 1 H, ArH).…”