Premium
Cyclodimerization of 1‐(Dimethoxyniethyl)‐5,6‐dimethylidene‐7‐oxa‐bicyclo[2.2.1]hept‐2‐ene Induced by Nonacarbonyldiiron. Crystal Structure of (1 RS , 2 SR , 3 RS , 4 RS , 4a RS , 9a SR )‐ Tricarbonyl[ C , 2,3, C ‐η‐(1,4‐epoxy‐1,5‐bis(dimethoxymethyl)‐2,3‐dimethylidene‐1,2,3,4,4a,9,9a,10‐octahydroanthracene)]iron
Author(s) -
Bonlantini Edia,
Vogel Pierre,
Pinkerton Alan A.
Publication year - 1989
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19890720506
Subject(s) - chemistry , moiety , diene , crystal structure , ene reaction , conformational isomerism , bicyclic molecule , stereochemistry , crystallography , acetal , carboxylate , medicinal chemistry , molecule , organic chemistry , natural rubber
The transition‐metal‐carbonyl‐induced cyclodimerization of 5,6‐dimethylidene‐7‐oxabicyclo[2.2.1]hept‐2‐ene is strongly affected by substitution at C(1) While 5,6‐dimethylidene‐7‐oxabicyclo[2.2.1]hept–2‐ene‐l‐methanol ( 7 ) refused to undergo [4 + 2]‐cyclodimerization in the presence of [Fe 2 (CO) 9 ] in MeOH, 1‐(dimethoxymethyl)‐5,6‐di‐methylidene‐7‐oxabicyclo[2.2.1]hept‐2‐ene ( 8 ) led to the formation of a 1.7:1 mixture of ‘trans’ ( 19, 21, 22 ) vs. ‘cis’ ( 20, 23, 24 ) products of cyclodimerization together with tricarbonyl[ C , 5,6, C ‐η‐(l‐(dimethoxymethyl)‐5,6‐di‐methylidenecyclohexa‐1,3‐diene)]iron ( 25 ) and tricarbonyl[ C ,3,4, C ‐η‐(methyl 5‐(dimethoxymethyl)‐3,4‐di‐methylidenecyclohexa‐1,5‐diene‐l‐carboxylate)]iron ( 26 ). The structures of products 19 and of its exo ( 21 ) and endo ( 22 ) [Fe(CO) 3 (1,3‐diene)]complexes) and 20 (and of its exo ( 23 ) and endo (24) (Fe(CO) 3 (1,3‐diene)complexes) were confirmed by X‐ray diffraction studies of crystalline (1 RS , 2 SR , 3 RS , 4 RS , 4a RS , 9a SR )‐tricarbonyl[ C , 2,3, C ‐η‐(1,4‐epoxy‐1,5‐bis(dimethoxymethyl])‐2,3‐dimethylidene‐1,2,3,4,4a,9,9a,10‐octahydroanthracene)iron ( 21 ). In the latter, the Fe(CO) 3 (1,3‐diene) moiety deviates significantly from the usual local C s symmetry. Complex 21 corresponds to a ‘frozen equilibrium’ of rotamers with η‐alkyl, η 3 ‐allyl bonding mode due to the acetal unit at the bridgehead centre C(1).