Synthesis of Chiral 1,3-Dienes through Ring-Closing Metathesis of Enantioenriched Enynes: Potential Precursors of Morphane Analogs

Abstract

A simple methodology for the synthesis of enynes by indium mediated diastereoselective allylation of aromatic N-tert-butanesulfinylimines bearing alkenyl groups at ortho-position with allyl bromide has been developed. The addition of the allyl indium intermediate to the chiral imine took place with excellent diastereoselectivity. Ruthenium-catalyzed ring-closing metathesis of the resulting enynes provided the expected cyclic 1,3-dienes in good to moderate yields. These chiral dienes are potential precursors of biologically and pharmacologically active morphane derivatives.

Pseudo-multicomponent 1,3-dipolar cycloaddition involving metal-free generation of unactivated azomethine ylides

“…The H a of 7 , as well as that of precursor 6 , remained in trans -arrangement with R 1 , which justified that no epimerization occurred at this stereogenic centre during the metathesis reaction. This fact is in agreement with the no epimerization detected in similar substrates during Rh-catalyzed cyclotrimerization is reported in the literature 11,14 ensure the relative configuration of 4 and 6 too.…”

“…in refluxing acetonitrile for 24 h using potassium carbonate as the base. Enynes 5 were isolated in very high yields and immediately subjected to ring-closing metathesis using the Grubbs II catalyst (20 mol%) under refluxing dichloromethane for 24 h. 14 Tricyclic dienes 6 were isolated in excellent yields and with high purity from the crude reaction mixture (Scheme 3). Next, the [4 + 2] cycloaddition took place in the presence of NPM at room temperature for 24 h, giving the desired pentacyclic scaffolds 7 in almost quantitative yields (91-94%) (Scheme 2).…”

“…13 C NMR (101 MHz) δ: 172.1 (CO), 170.9 (CO), 139.6 (ArC), 128.1 (ArCH), 127.9 (ArCH), 127.7 (ArCH), 82.3 (CuCH), 73.3 (CuCH), 62.8 (NCHAr), 52.4 (CH 3 ), 51.6 (CH 3 ), 51.1 (CHCO), 50.9 (CHCO), 49.9 (NCHCuCH). LRMS (EI) m/z: 287 (M + , 1%), 104 (11), 115 (41), 116 (19), 119 (13), 125 (50), 142 (39), 143 (68), 146 (15), 167 (12), 168 (14), 177 (100), 178 (12), 256 (16). HRMS (ESI) calcd for C 16 H 17 NO 4 : 287.1158; found: 287.1137.…”

Chiral N‐tert‐Butylsulfinyl Imines: New Discoveries

“…The N ‐allylation of compounds 239 followed by ring‐closing metathesis led to the formation of the corresponding bicyclic dienes, able to perform Diels‐Alder reactions [141] . The corresponding N ‐propargylation of 239 yielded diynes 244 , which after oxidation to compounds 245 , reacted with an acetylene in the presence of a Rh catalyst, to give the corresponding tetrahydroisoquinolines 246 (Scheme 104).…”