Synthesis of (R)‐ and (S)‐Aldehydes and ‐Ketones from Chiral sec‐Alkyl Halides

Abstract

stirred vigorously at 20 "C for 16 h, and then at 65 "C for 1.5 h. The mixture is filtered while hot and the residue is washed with CH30H. The filtrate is diluted with water and extracted with pentane[W Crude yield of (8f) 2.05 g, [ O L ] ;~ = +13.6 (c = 4, ether). Distillation affords 1.67 g of (Sf) (overall yield calculated with respect t o (61, 51.4 %), b.p. 65-68 'C/7 torr, n'," = 1.4232, [m]L3 = +13.4 (c = 5 , ether) [corresponds to +22.4 calculated with respect to optically pure ( 6 A . Ketones and aldehydes of type ( 1 ) are valuable for mecha-1.4248, [a]'," = -13.2 (c = 5 , ether).

Acyl anion equivalents. Synthesis of ketones and α-(phenylthio)ketones from the adducts of bis(phenylthio)carbanions and carbonyl compounds

“…There are discouraging reports in the literature * on both the metallation of the alkylated compounds (10) and on the reaction of the resulting anions with carbonyl compounds. We have found that orange anions are formed by treatment with BuLi in THF in the presence of NNN' N'-te tramet hylethylenediamine (TMEDA) for 15 min at 0 "C. (14).-When the aldehyde adducts (14) are dissolved in TFA at room temperature, reaction is instantaneous: an n.m.r. spectrum of the solution usually shows only diphenyl disulphide and the ketone (15).…”

“…and 110 (PhSH, 100) (Found: C, 66.3; H , 6.5; S, 21.9. C16H1,OSz requires C, 66.2; H, 6.24; S, (14; R1 = Me, R2 = Et).…”

“…The extract was washed with water (5 ml), dried (MgSO,), and evaporated to give the alcohol (144 mg, 1OOyo) as an oil, RF (CH,Cl,) 0.52, umx. (14; R1 = Me, R2 = Ph). 1,l-Bis(pheny1thio)ethane (0.62 g, 2.5 mmol), TMEDA (0.31 g, 2.7 mmol), n-butyl-lithium (1.54~ in hexane; 1.9 ml, 2.9 mmol), and benzaldehyde (0.27 g, 2.5…”

“…Synthesis of Ketones from Aldehyde Adducts (14) .-Pentan-2-one. The alcohol (14; R1 = Me, R2 = Et) (100 mg) was dissolved in TFA (0.4 ml) in an n.m.r.…”