55170-74-6Relevant articles and documents
Asymmetric Evans syn-Aldol Reactions of Terpene-Derived Enals: Scope and Limitations
Kriening, Sebastian,Evagelou, Athanasios,Claasen, Birgit,Baro, Angelika,Laschat, Sabine
, p. 6720 - 6733 (2014)
The (E)- and (Z)-terpene-based aldehydes 6b and 6c with a silyl ether function in the γ-position were prepared and investigated in boron-mediated asymmetric Evans aldol reactions. Screening experiments of chiral N-acylated oxazolidinones 7, which are conveniently accessible from 5-methyl-5-hexenoic acid and Evans oxazolidinone auxiliaries, with various boron triflates and terpenoid neral (Z)-6a as aldehyde component, provided conditions in which highly selective formation of syn-aldol adduct 5a occurred and competing C=C double bond isomerization to 10 was completely suppressed. Applying the optimized conditions to O-silylated aldehydes 6b and 6c and N-acyloxazolidinone derivative (R)-7a confirmed the syn-selectivity and gave the appropriate products syn-5b,c and syn-21b,c in good yields. In the case of neral-derived syn adduct 5a, the configuration of the new stereogenic centers C-2/C-3 could be assigned as (2R,3S). The asymmetric Evans aldol reaction could be successfully applied to terpene-based (E)- and (Z)-aldehydes and N-acyloxazolidinones, giving syn-aldol adducts with high selectivity. Isomerization at the double bond was not observed.
Oxidative Cleavage of Alkenes by O2with a Non-Heme Manganese Catalyst
Bennett, Elliot L.,Brookfield, Adam,Guan, Renpeng,Huang, Zhiliang,Mcinnes, Eric J. L.,Robertson, Craig M.,Shanmugam, Muralidharan,Xiao, Jianliang
, p. 10005 - 10013 (2021/07/19)
The oxidative cleavage of C═C double bonds with molecular oxygen to produce carbonyl compounds is an important transformation in chemical and pharmaceutical synthesis. In nature, enzymes containing the first-row transition metals, particularly heme and non-heme iron-dependent enzymes, readily activate O2 and oxidatively cleave C═C bonds with exquisite precision under ambient conditions. The reaction remains challenging for synthetic chemists, however. There are only a small number of known synthetic metal catalysts that allow for the oxidative cleavage of alkenes at an atmospheric pressure of O2, with very few known to catalyze the cleavage of nonactivated alkenes. In this work, we describe a light-driven, Mn-catalyzed protocol for the selective oxidation of alkenes to carbonyls under 1 atm of O2. For the first time, aromatic as well as various nonactivated aliphatic alkenes could be oxidized to afford ketones and aldehydes under clean, mild conditions with a first row, biorelevant metal catalyst. Moreover, the protocol shows a very good functional group tolerance. Mechanistic investigation suggests that Mn-oxo species, including an asymmetric, mixed-valent bis(μ-oxo)-Mn(III,IV) complex, are involved in the oxidation, and the solvent methanol participates in O2 activation that leads to the formation of the oxo species.
SYNTHESIS OF CANNABINOIDS
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, (2019/02/05)
Provided are synthesis processes and intermediates for preparing cannabinoids and analogs.
