Predictable Stereoselective and Chemoselective Hydroxylations and Epoxidations with P450 3A4
摘要:
Enantioselective hydroxylation of one specific methylene in the presence of many similar groups is debatably the most challenging chemical transformation. Although chemists have recently made progress toward the hydroxylation of inactivated C-H bonds, enzymes such as P450s (CYPs) remain unsurpassed in specificity and scope. The substrate promiscuity of many P450s is desirable for synthetic applications; however, the inability to predict the products of these enzymatic reactions is impeding advancement. We demonstrate here the utility of a chemical auxiliary to control the selectivity of CYP3A4 reactions. When linked to substrates, inexpensive, achiral theobromine directs the reaction to produce hydroxylation or epoxidation at the fourth carbon from the auxiliary with pro-R facial selectivity. This strategy provides a versatile yet controllable system for regio-, chemo-, and stereoselective oxidations at inactivated C-H bonds and demonstrates the utility of chemical auxiliaries to mediate the activity of highly promiscuous enzymes.
Palladium-Catalyzed, Ring-Forming Aromatic C–H Alkylations with Unactivated Alkyl Halides
作者:Alexander R. O. Venning、Patrick T. Bohan、Erik J. Alexanian
DOI:10.1021/jacs.5b01365
日期:2015.3.25
using unactivated alkylhalides and a variety of arenes and heteroarenes is described. This ring-forming process is successful with a variety of unactivated primary and secondaryalkylhalides, including those with β-hydrogens. In contrast to standard polar or radical cyclizations of aromatic systems, electronic activation of the substrate is not required. The mild, catalytic reaction conditions are highly
Metallaphotoredox-catalysed sp3–sp3 cross-coupling of carboxylic acids with alkyl halides
作者:Craig P. Johnston、Russell T. Smith、Simon Allmendinger、David W. C. MacMillan
DOI:10.1038/nature19056
日期:2016.8
remains an important yet elusive objective for engineering cross-coupling reactions. In comparison to related procedures with sp2-hybridized species, the development of methods for sp3–sp3 bondformation via transition metal catalysis has been hampered historically by deleterious side-reactions, such as β-hydride elimination with palladium catalysis or the reluctance of alkyl halides to undergo oxidative
Olefin Epoxidation with Bis(trimethylsilyl) Peroxide Catalyzed by Inorganic Oxorhenium Derivatives. Controlled Release of Hydrogen Peroxide
作者:Andrei K. Yudin、Jay P. Chiang、Hans Adolfsson、Christophe Copéret
DOI:10.1021/jo010369m
日期:2001.6.1
using bis(trimethylsilyl) peroxide (BTSP) as oxidant in place of aqueous H(2)O(2). Using a catalytic amount of a proton source, controlled release of hydrogen peroxide helps preserve sensitive peroxorhenium species and enables catalytic turnover to take place. Systematic investigation of the oxorheniumcatalyst precursors, substrate scope, and effects of various additives on olefinepoxidation with
intramolecular ortho-alkylation proceeds in a domino process with various termination steps, generating two new carbon−carbon or carbon−nitrogen bonds in one pot, to afford an array of polycyclic heterocycles. The use of enantioenriched substrates has shown that this palladium-catalyzed reaction is stereospecific, proceeding with minimal erosion of ee.
Reductive Spiroannulation of Nitriles with Secondary Electrophiles
作者:Matthew D. Morin、Scott D. Rychnovsky
DOI:10.1021/ol050567q
日期:2005.5.1
The scope of reductive decyanation and spiroannulation reactions has been expanded to include secondary electrophiles for potentially useful transformations. Secondary phosphates and chlorides, as well as terminal epoxides, cyclize in a stereospecific fashion. Both endo and exo modes of cyclization were observed with terminal epoxides.