P-Donor-substituted a$-unsaturated chromium carbene cornplexes (CO),CrC(OEt)C = CR(XR',) (X = N, 0, S; 3, 9, 11 -16, 22 -25) have been synthesized by Michael addition of amines, alcohols, and thiols to alkynylcarbene complexes (CO),CrC-(0Et)C = CR (1). The configurations of the newly formed C -C double bonds have been determined by NOE/NOESY measurements and X-ray crystal structure analysis. These vinylcarbene complexes lose one carbonyl ligand in refluxing tetrahydrofuran to give tetracarbonyl complexes (CO),CrC(OEt)-C = CR(XR,) (X = N, 0, S; 26 -28).
sung aufeine Natriunihydrogcnc;irhon;it-l.li\ung. wiischt die orgnnischc Pha\e mit W i s e r . trocknct uhcr Y:i2S0,. engt riii und erhilt 34 5 g 7 (75%). Fp = 110 112 c'. (Die \V:isser;ih\paltun@erfi,lpf m;inchm;il rechf bpoiitan und ~oIIte dahcr in eincm grolkn. rndxiniiil i u r Ii.ilfte pefullten Kolhcn erfolgen)
Only products with severely restricted substitution patterns could be produced, and in low yields, by the multistep syntheses previously known for the pseudoazulenes. In contrast, the easily obtained vinylcarbenechromium complex 1 described here offers a simple high‐yield access to the cyclopenta[b]pyranes 2 when a quaternary group occupies the β‐position. The X‐ray structural analysis shows that the rings of the heterobicycle 2 deviate from planarity by a mere 3.7o.
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