Facial Stereoselectivity in the Diels−Alder Reactions of (Arylethynyl)ethoxycarbenes of Group 6 with 1,2,3,4,5-Pentamethylcyclopenta-1,3-diene and Unusual Rearrangement of Strained Norbornadienyl Fischer Carbene Complexes of Chromium(0)

This is the authors' abstract. We don't add key points for this paper.

A study of reactivity and facial selectivity in Diels−Alder reactions of the Fischer carbene complexes (CO) 5 M C(C⋮CC 6 H 4 R)OCH 2 CH 3 ( 1a, M = Cr, R = H; 1b, M = Cr, R = p -OCH 3; 1c, M = Cr, R = p -CH 3; 2, M = W, R = H; 3, M = Mo, R = H), with 1,2,3,4,5-pentamethylcyclopenta-1,3-diene ( 4 ) was carried out. The cycloadditions were found to be highly π-facial stereoselective, favoring the anti adduct. Among these complexes, 3 was the most reactive dienophile. The stereochemical assignment of the adducts 5 − 7 was supported by NOE measurements; structures of the anti cycloadducts 5a and 6 were established by single-crystal X-ray diffraction. A [4 + 2] cycloaddition/benzannulation/rearrangement cascade reaction was observed for the chromium carbene complexes 1a − c with 4 under thermal conditions, resulting in the naphthofurandione derivatives 9 − 11 .