Chiral Mo−Binol Complexes:  Activity, Synthesis, and Structure. Efficient Enantioselective Six-Membered Ring Synthesis through Catalytic Metathesis

Abstract

A new class of chiral Mo-based complexes 2a and 2b, bearing functionalized chiral binol ligands, is disclosed. Mo complex 2a promotes the asymmetric ring-closing metathesis (ARCM) of various dienes and trienes to afford six-membered carbo- and heterocycles efficiently and in high optical purity. The binol-based chiral Mo catalysts complement the previously reported biphen-based complexes, which are particularly effective in the enantioselective synthesis of five-membered rings by ARCM. Studies regarding catalytic kinetic resolutions and asymmetric desymmetrizations are described. It is possible to obtain optically pure products in high yield from catalytic reactions without the use of solvent (cf. eq 1). The structural attributes of these complexes are detailed on the basis of the data available from an X-ray structure and variable-temperature 1H NMR studies. The results of this investigation indicate the following: (i) The anti-Mo·THF complex exists as a mixture of diastereomers, whereas the syn isomer is formed stereoselectively. (ii) The anti-Mo isomers are likely more Lewis acidic.

Temporary Silicon‐Tethered Ring‐Closing Metathesis: Recent Advances in Methodology Development and Natural Product Synthesis

“…The stereochemistry has been determined by a strong NOE correlation between H15 and H18 which is consistent with a (15S,18R) configuration as required in the natural product 69. [36] Relay ring-closing metathesis: Hoye and co-workers recently reported the application of a temporary silicon-tethered relay ring-closing metathesis (TST-RRCM) strategy in the total synthesis of peloruside A (69). [37] The RRCM reaction is a relatively recent concept and represents a supplement to traditional RCM reaction.…”

The Directed Ortho Metallation (DoM)–Cross‐Coupling Nexus. Synthetic Methodology for the Formation of Aryl–Aryl and Aryl–Heteroatom–Aryl Bonds

“…With some exceptions [110], systematic studies of efficacy comparisons of the [111][112][113], the DoM-cross-coupling sequence represents a significant entry into chiral binaphthol (BINOL) and achiral biphenol (BIPOL) ligands (Table 14.18) [111][112][113][114][115][116][117][118][119], which are outside the scope of this review but are widely used for enantioselective reactions, for example, Et 2 Zn addition to aromatic aldehydes, the Mannich-type reactions, and the Diels-Alder as well as asymmetric ring-closing metathesis (ARCM) reactions. …”

Bio‐Inspired Transfer Hydrogenations

“…The synthesis of the chiral BINOL phosphate derivatives is straightforward [11c-e, [16][17][18][19][20][21][22]. For example, Rueping reported the synthesis of 5 starting from the protected (R)-3,3 -dibromo-1,1 -binaphthyl-2,2 -diol and its octahydro analog derivative 4a, which are obtained from BINOL and H (Scheme 22.2).…”

“…A similar approach towards this class of compounds was reported by Akiyama and involves Suzuki coupling of a bis(boronic acid) binaphthol derivative with different aryl halides [18], deprotection, and phosphorylation [16b]. The synthesis of the 3,3 -bis(2,4,6-triisopropylphenyl) BINOL derivative required for the preparation of 5e can be accomplished according to Schrock [20]. The silylated Brønsted acids 6 can be synthesized following a procedure reported by Yamamoto [21] and MacMillan [22], which involves a Brook-type-rearrangement of the BINOL-derivative 4b using t-BuLi and subsequent phosphorylation.…”