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Indenylidene Complexes of Ruthenium: Optimized Synthesis, Structure Elucidation, and Performance as Catalysts for Olefin Metathesis—Application to the Synthesis of the ADE‐Ring System of Nakadomarin A
Author(s) -
Fürstner Alois,
Guth Oliver,
Düffels Arno,
Seidel Günter,
Liebl Monika,
Gabor Barbara,
Mynott Richard
Publication year - 2001
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/1521-3765(20011119)7:22<4811::aid-chem4811>3.0.co;2-p
Subject(s) - olefin metathesis , ruthenium , ring (chemistry) , catalysis , metathesis , olefin fiber , combinatorial chemistry , acyclic diene metathesis , ring opening metathesis polymerisation , chemistry , organic chemistry , polymerization , polymer
An optimized and large scale adaptable synthesis of the ruthenium phenylindenylidene complex 3 is described which employs commercially available diphenyl propargyl alcohol 5 as a stable and convenient carbene source. Previous ambiguities as to the actual structure of the complex have been ruled out by a full analysis of its NMR spectra. A series of applications to ring closing metathesis (RCM) reactions shows that complex 3 is as good as or even superior to the classical Grubbs carbene 1 in terms of yield, reaction rate, and tolerance towards polar functional groups. Complex 3 turns out to be the catalyst of choice for the synthesis of the enantiopure core segment 77 of the marine alkaloid nakadomarin A 60 comprising the ADE rings of this target. Together with a series of other examples, this particular application illustrates that catalyst 3 is particularly well suited for the cyclization of medium‐sized rings by RCM. Other key steps en route to nakadomarin A are a highly selective intramolecular Michael addition setting the quaternary center at the juncture of the A and D rings and a Takai–Nozaki olefination of aldehyde 73 with CH 2 I 2 , Ti(O i Pr) 4 and activated zinc dust.