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Synthesis of 2‐ and 3‐Stannolenes via Addition of Trimethyltin Alkoxides to 3‐Diethylboryl‐4‐ethyl‐1,1‐dimethylstannole
Author(s) -
Wrackmeyer Bernd,
Klaus Uwe,
Milius Wolfgang
Publication year - 1995
Publication title -
chemische berichte
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 0009-2940
DOI - 10.1002/cber.19951280705
Subject(s) - chemistry , geminal , heteronuclear molecule , allylic rearrangement , stereochemistry , group (periodic table) , crystallography , crystal structure , boron , medicinal chemistry , nuclear magnetic resonance spectroscopy , catalysis , organic chemistry
Trimethyltin alkoxides ( 2 ) react stereoselectively with 3‐diethylboryl‐4‐ethyl‐1,1‐dimethylstannole ( 1 ) via addition of the Me 3 Sn group to C(2) to the C(2) = C(3) bond and a 1,2 shift of an ethyl group from boron to C(3) to give the 2‐stannolenes 3. The molecular structure of 3f' [R = ( S )‐2‐Bu] was determined by single‐crystal X‐ray analysis, confirming the cis positions of the Et(RO)B and the Me 3 Sn group. These 2‐stannolenes 3 undergo, upon heating to ca. 80°C, facile rearrangement by irreversible allylic migration of the Et(RO)B group to the 3‐stannolenes 4 in which the cis positions of the boryl and the stannyl group are retained. All 2‐stannolenes (in contrast to the 3‐stannolenes) are readily deprotoborylated to give the 3‐stannolene 5. The structures of 3 , 4 , and 5 follow conclusively from 1 H‐, 11 B‐, 13 C‐, and 119 Sn‐NMR spectra. The negative sign of the geminal coupling constants 2 J (SnSn) was determined in the case of 3 , 4 , and 5 by 2D 119 Sn/ 1 H heteronuclear shift correlations.