Naturalproductman’s Blog

Hey, is that a natural product?!

Archive for September, 2009

New Fe Catalyzed C-C Bond Forming Processes

Posted by naturalproductman on September 30, 2009

Zhang-Jie Shi et al at Peking University have recently published in JACS on an iron catalyzed Grignard and alkenyl carboxylate coupling strategy.  Something odd in the paper is that in the introduction they mention that the advantage of using an alkenyl/aryl carboxylate over using a halide is that it is easier to make and it’s not as bad for the environment – however, ironically the Grignard reagent that they use is also made from a halide so I don’t know if I would have mentioned that in the paper.  They use a carbene ligand with the iron catalyst.  In their screen studies they show that triphenylphosphine works as well.

fe
At the same time of this publication came another iron catalyzed cross coupling reaction that involved the coupling of a tosylate with a Grignard using also an iron catalyst.  Troels Skrydstru at Aarhus University in Denmark have reported this reaction.

tosylate


JACS paper

OL paper

Posted in Carbene, cross coupling, Methodology, Transition Metal | Leave a Comment »

Multicomponent coupling

Posted by naturalproductman on September 30, 2009

Liu-Zhu Gong et al at the University of Science and Technology in China have recently published in JACS on a Biginelli like reaction catalyzed by a C2 symmetric BINAP Bronstead acid.

biginelli
JACS paper

Posted in Asymmetric, Methodology, Multi-Component Coupling, Ring forming | Leave a Comment »

Alkyne Aza Prins

Posted by naturalproductman on September 30, 2009

Young Ho Rhee and co-workers at POSTECH in Korea have recently published in JACS on a unique cascade reaction catalyzed by a gold complex.  The transformation involves the formation of an alkynyl-iminium intermediate.

cascade


JACS paper

Posted in Alkaloids, Cascade Reactions, Mechanistic, Methodology, Ring forming, Transition Metal | Leave a Comment »

Is that a Diterpene?

Posted by naturalproductman on September 28, 2009

Telma Leos and co-workers at the Universidade Federal do Ceara in Brazil have recently published in the Journal of Natural Products on their isolation of three diterpenes from a bark of Croton argyrophylloides.  The most active one seems to be at the most ten times more active than doxorubicin against human tumor cell lines plus it is already a known compound:  HL-60 (leukemia), MDAMB-435 (melanoma), SF-
295 (glioblastoma), and HCT-8 (colon carcinoma) with IC50s ranging in the low micromolar range.  However the lactone moiety seems necessary since in the absence of it, the new compounds are not active at all (ie:  IC50 is greater than 10 micromolar).

diterpenes

JNP paper

Posted in Diterpene, Diterpenoids | Leave a Comment »

What’s the Mechanism?

Posted by naturalproductman on September 28, 2009

The research group of Dean Tantillo, a physical organic chemist at UC Davis, has collaborated with Janis Louie’s group in Utah to understand the mechanism of a Ni-carbene-complex-catalyzed rearrangement of a vinylcyclopropane to cyclopentene rearrangement; their findings were reported in JOC.  One of the intermediates involves a Ni-pi allyl complex.  The first order rate constants were determined by NMR using a ferrocene complex as an internal standard.  This NIH supported research seems to provide valuable insight on how to approach a problem such as figuring out a mechanism to a complex reaction.

Ni


JOC paper

Posted in Mechanistic, Methodology, Ring forming, Transition Metal | Leave a Comment »

Simple Fluorination

Posted by naturalproductman on September 25, 2009

Fluorinations are known to be a tough reaction to accomplish – in other words, many of the ways to fluorinate compounds required harsh conditions.  That’s why Buchwald’s paper recently appears in Science where he converts aryl triflates to aryl fluorides using a palladium catalyst and a fluoride source (cesium fluoride).  Fluorinations have been an area of focus for Tobias Ritter at Harvard as well and many of his recent papers in JACS and ACIEE have been on this deceptively simple transformation.

fluorination
Science paper

Posted in Aromatic, cross coupling, Methodology, Transition Metal | Leave a Comment »

Cytochrome P450 Inhibitors

Posted by naturalproductman on September 21, 2009

James McNulty and co-workers at McMaster University in Canada have recently published in Bioorganic and Medicinal Chemistry Letters on an SAR study to find potent cytochrome P450 3A4 inhibitors.

cytochrome p450


Bioorganic and Medicinal Chemistry Letters paper

Posted in Alkaloids | Leave a Comment »

An Electrophilic Bromine Source

Posted by naturalproductman on September 21, 2009

Scott Snyder and Treitler from Columbia have recently published in ACIEE on a new electrophilic bromine source to induce a pi-cation cyclization reaction.

bromine source

ACIEE paper

Posted in Cascade Reactions, Methodology, Ring forming | Leave a Comment »

Asymmetric/Catalytic Cr-Mediated Propargylation

Posted by naturalproductman on September 19, 2009

Kishi (Harvard) and co-workers have published in Org Lett recently on a modification of an NHK reaction using a sulfonamide chiral ligand on a Cr catalyst to couple a propargyl bromide onto an aldehyde.

cr propargylation

OL paper

Posted in Allenes, Asymmetric, Methodology, Transition Metal | Leave a Comment »

N-Heterocyclic Carbene Catalyzed

Posted by naturalproductman on September 17, 2009

From what I know hydroacylations accross olefins are not too common and usually what’s been done is a hydroacylation of an aldehyde using a transition metal such as rhodium.  Recently Frank Glorius and co-workers from Organisch-Chemisches Institut der Westfalischen Wilhelms-Universitat Munster have published in JACS on an intramolecular hydroacylation reaction using an N-heterocyclic carbene catalyst.

carbene


JACS paper

Posted in Carbene, Cascade Reactions, Methodology, Organocatalytic | Leave a Comment »

 
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