No abstract

Die IR‐Spektren der Verbindungen (I) werden angegeben.

Ein elektrophiles C‐Atom kennzeichnet die beiden Titelsulfene im Unterschied zu anderen Sulfenen, bei denen das S‐Atom elektrophil ist. Dies folgt aus den Strukturen der Et3N‐Addukte, die in diesen Fällen als Zwitterionen 1 bzw. 2 vorliegen und nicht der allgemeinen Struktur A entsprechen. 2 entsteht aus FH2C‐SO2Cl und Et3N, 1 durch Aminolyse des Dithietans 3.

R2 0 CH2OH l a , b 7 + 8a, b P 9 3a, b Received: October 12, 1988 [3006 IE] German version: Angew. Chem. 101 (1989) 224 CAS Registry numbers: 3, 795-31-3: 4, 118724-94-0; 5, 767-45-3: 6, 118724-95-1; quinuclidine, 100-76-5.

rnate.I4] The Grignard reagent 3 consists of an equilibrium mixture of enantiomers, diastereomers, and conformational isomers owing to rotation around formal single bondsrs] and 1,3-metallotropic shift.[61 Borate 4 reacts preferentially with 3 b, brr7] to afford an 89 % yield of the pentenylboronic esters 1 and 5, which have (Z) configurations (cf. Ref. [S]). v 5 Furthermore, the chiral borate 4 differentiates between the enantiomers 3b,b', so that 1 can be obtained with a diastereomeric excess of 94 % by kinetic resolution of a racemate. This was established by reaction of 1 with benzaldehyde and determination of the enantiomeric purity of alcohol 2. The glycol from which 4 is derived and thus the reagent 1 are readily accessible in either enantiomeric Experimental ProcedureA 0.85 M solution (6.0 mL, 5.1 mmol) of (1-methyl-2-buteny1)magnesium chloride (3) in THF was added dropwise over 15 min to a solution of (4S,5s)-2-isopropyloxy-4,5-dicyclohexyl-1,3,2-dioxaborolane (4; prepared from 1,2-dicycIohexylethane-l,2-diol and triisopropyl borate by distillative removal of the isopropanol) in 20 mL of THF at -78 "C. The solution was allowed to warm overnight to room temperature and the products were hydrolyzed by addition of a saturated solution (1 5 mL) of NH,CI. The aqueous phase was extracted with 3 x 20 mL of ether and the organic phase was dried over MgSO, and concentrated. The colorless oily residue was chromatographed with CH,Cl, (column 30 x 2 cm, silica gel 60), affording 1.38 g (89 YO) of boronic ester 1. For spectroscopic data and determination of the enantiomeric purity by addition to benzaldehyde, see 12). 0 VCH Verlagsgesellschaft mbH, 0-6940 Wemherm, 1990 0570-0833190~0lOl-0061 $ 0 2 SO10