Allylic Carbamates Research Articles

ChemInform Abstract: An Efficient Convergent Synthesis of 1α,25‐Dihydroxy‐3‐epi‐Vitamin D2

AbstractReview: 11 refs.

ChemInform Abstract: Substrate Scope and Stereocontrol in the Rh(II)‐Catalyzed Oxyamination of Allylic Carbamates.

AbstractA procedure for the acetoxyamination of a broad range of allylic carbamates is established.

ChemInform Abstract: Enantioselective Transformation of Allyl Carbonates into Branched Allyl Carbamates by Using Amines and Recycling CO2 under Iridium Catalysis.

AbstractA domino reaction of allyl carbonates and amines is developed to yield enantioenriched branched allyl carbonates.

Progress towards bioorthogonal catalysis with organometallic compounds.

The catalysis of bioorthogonal transformations inside living organisms is a formidable challenge--yet bears great potential for future applications in chemical biology and medicinal chemistry. We herein disclose highly active organometallic ruthenium complexes for bioorthogonal catalysis under biologically relevant conditions and inside living cells. The catalysts uncage allyl carbamate protected amines with unprecedented high turnover numbers of up to 270 cycles in the presence of water, air, and millimolar concentrations of thiols. By live-cell imaging of HeLa cells and with the aid of a caged fluorescent probe we could reveal a rapid development of intense fluorescence within the cellular cytoplasm and therefore support the proposed bioorthogonality of the catalysts. In addition, to illustrate the manifold applications of bioorthogonal catalysis, we developed a method for catalytic in-cell activation of a caged anticancer drug, which efficiently induced apoptosis in HeLa cells.

An efficient nonisocyanate route to polyurethanes via thiol‐ene self‐addition

ABSTRACTA novel and efficient strategy for the synthesis of nonisocyanate polyurethanes has been developed via thiol–ene self‐photopolymerization. An aliphatic thiol–ene carbamate monomer (allyl(2‐mercaptoethyl)carbamate, AMC) was synthesized by a one‐step synthesis procedure, from cysteamine and allyl chloroformate. The urethane group was therefore incorporated directly into the monomer precursor, avoiding the problems associated to toxic isocyanates. AMC was successfully stabilized with the radical inhibitor pyrogallol (1% wt). In addition, the use of phenyl phosphonic acid as coadditive allowed its stabilization for lower concentrations of pyrogallol (0.1% wt). AMC was directly transformed into thermoplastic polyurethane (TPU) through thiol–ene photopolymerization by UV‐irradiation at 365 nm. The obtained TPU presented semi‐crystalline nature and very high thermal stability (T5% ∼325 °C). It was found that high concentrations of pyrogallol decreased the reaction rate and final conversion of photopolymerization. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 3017–3025

ChemInform Abstract: Lipase‐Catalyzed Desymmetrization of meso‐1,2‐Diaryl‐1,2‐diaminoethanes.

Abstract The synthesis and enzyme-catalyzed desymmetrization of meso-1,2-diaryl-1,2-diaminoethanes have been investigated. A family of aromatic meso-1,2-diamines, containing different substitution patterns in the aromatic ring, was first prepared and then desymmetrized enantioselectively using lipases as biocatalysts. Selective alkoxycarbonylation of one of the amino groups was achieved using allyl carbonates, isolating the corresponding allyl monocarbamates with moderate to high enantiomeric excess at 45 °C. Candida antarctica lipase types A (CAL-A) and B (CAL-B) displayed the best activities and stereopreferences, with a dramatic influence being observed depending on the diamine structure. Non substituted and para-substituted aryldiamines led to the formation of allyl carbamates with good enantiomeric excess, using CAL-A for the less hindered substrates and CAL-B for the more hindered ones. On the other hand meta- and ortho-derivatives afforded low or negligible conversions and selectivities, respectively.

Substrate scope and stereocontrol in the Rh(II)-catalysed oxyamination of allylic carbamates

Application of a modified Du Bois protocol for rhodium-stabilised nitrenoid generation to a variety of allylic carbamates results in 4-acetoxymethyl-1,3-oxazolidin-2-one derivatives with moderate to high levels of stereocontrol.

Asymmetric cascade reaction to allylic sulfonamides from allylic alcohols by palladium(II)/base-catalyzed rearrangement of allylic carbamates.

A regio- and enantioselective tandem reaction is reported capable of directly transforming readily accessible achiral allylic alcohols into chiral sulfonyl-protected allylic amines. The reaction is catalyzed by the cooperative action of a chiral ferrocene palladacycle and a tertiary amine base and combines high step-economy with operational simplicity (e.g. no need for inert-gas atmosphere or catalyst activation). Mechanistic studies support a Pd(II)-catalyzed [3,3] rearrangement of allylic carbamates--generated in situ from the allylic alcohol and an isocyanate--as the key step, which is followed by a decarboxylation.

Enantioselective transformation of allyl carbonates into branched allyl carbamates by using amines and recycling CO2 under iridium catalysis.

Enantioselective transformation of allyl carbonates into branched allyl carbamates by using amines and recycling CO2 in the presence of an Ir complex and K3PO4 was accomplished. This provided branched allyl carbamates in fair to excellent yields with up to 98:2 regioselectivity and 93 % ee. The role of CO2 in this transformation is discussed as well.

Progress toward a novel pro‐drug approach for temporal manipulation of protein kinase A with a commercially available ruthenium catalyst (968.1)

Transition metal catalysts have been demonstrated in principle for temporal and spatial control of reactions, but this technology has yet to be broadly applied as a tool for biological study and cellular manipulation. Here we demonstrate the use of a ruthenium complex catalyst as a novel approach for spatial and temporal release of a pro‐drug inside cells, namely the transition of caged H89 to active H89, a Protein Kinase A (PKA) inhibitor. We synthesized caged H89 by protecting H89 as an allyl carbamate. We designed the system to intracellularly generate an active H89 inhibitor from caged H89 following addition of the ruthenium metal catalyst with the goal of inhibiting the catalytic activity of PKA and therefore reducing the phosphorylation of perilipin 1. The ruthenium catalyst activity was monitored by assessing the phosphorylation of perilipin 1, which is phosphorylated by PKA on 6 serine residues and not phosphorylated by other kinases. Experiments were performed on cell lines expressing endogenous perlipin 1, differentiated 3T3L1 cells and Y1 adrenal cells. Our results show that in its active state, H89 inhibited phosphorylation activity of PKA on substrates such as perilipin whereas the caged form of H89 lacked inhibitory activity. Experiments are planned for use of the ruthenium catalyst after the H89 and caged H89 incubation steps to determine the ability of the catalyst to activate caged H89 intracellularly.Grant Funding Source: Supported by The Royal Society of Chemistry

Lipase-catalyzed desymmetrization of meso-1,2-diaryl-1,2-diaminoethanes

The synthesis and enzyme-catalyzed desymmetrization of meso-1,2-diaryl-1,2-diaminoethanes have been investigated. A family of aromatic meso-1,2-diamines, containing different substitution patterns in the aromatic ring, was first prepared and then desymmetrized enantioselectively using lipases as biocatalysts. Selective alkoxycarbonylation of one of the amino groups was achieved using allyl carbonates, isolating the corresponding allyl monocarbamates with moderate to high enantiomeric excess at 45°C. Candida antarctica lipase types A (CAL-A) and B (CAL-B) displayed the best activities and stereopreferences, with a dramatic influence being observed depending on the diamine structure. Non substituted and para-substituted aryldiamines led to the formation of allyl carbamates with good enantiomeric excess, using CAL-A for the less hindered substrates and CAL-B for the more hindered ones. On the other hand meta- and ortho-derivatives afforded low or negligible conversions and selectivities, respectively.

Enantioselective domino reaction of CO2, amines and allyl chlorides under iridium catalysis: formation of allyl carbamates

The enantioselective domino reaction between CO2 (1 atm), amines and linear allyl chlorides in the presence of an iridium complex, DABCO and toluene at 15 °C was realized, which gave branched allyl carbamates in acceptable to high yields with up to excellent regioselectivity (99/1) and 94% ee. This is the first example of the synthesis of chiral allyl carbamates through catalytic domino reactions using CO2.

ChemInform Abstract: Microwave‐Assisted Expeditious Synthesis of 5‐Fluoroalkyl‐3‐(aryl/alkyl)‐oxazolidin‐2‐ones.

An efficient and convenient protocol for synthesis of 5-fluoroalkyl-3-(aryl/alkyl)-oxazolidin-2-ones is described. The reaction of allyl (aryl/alkyl) carbamates with fluoroalkyl iodide initiated by sodium dithionite in aqueous acetonitrile resulted in adducts that undergoes a cyclization assisted by microwave irradiation to form 5-fluoroalkyl-3-(aryl/alkyl)-oxazolidin-2-ones with high yields. It was also found that the products can be more efficiently formed via an AIBN-initiated one-pot addition–cyclization sequence from benzyl allyl(aryl/alkyl) carbamates and fluoroalkyl iodide.

ChemInform Abstract: Diastereoselective Intramolecular Allyl Transfer from Allyl Carbamate Accompanied by 5‐endo‐Trig Ring Closure.

AbstractKnoevenagel condensation of substrates (I) or (IX) with aromatic aldehydes followed by diastereoselective cyclization yields an unseparable mixture of highly functionalized pyrrolidin‐3‐ones in a one‐pot fashion.

Asymmetric Formal Synthesis of (–)‐Swainsonine by a Highly Regioselective and Diastereoselective Allylic Amination Using Chlorosulfonyl Isocyanate

AbstractA concise asymmetric formal synthesis of (–)‐swainsonine from readily available D‐erythronolactone is described. The key steps include a highly diastereoselective amination of a chiral benzylic ether, which occurs with the retention of stereochemistry using chlorosulfonyl isocyanate, and a palladium‐catalyzed decarboxylative N‐allylation of an allyl carbamate.

Microwave-assisted expeditious synthesis of 5-fluoroalkyl-3-(aryl/alkyl)-oxazolidin-2-ones

An efficient and convenient protocol for synthesis of 5-fluoroalkyl-3-(aryl/alkyl)-oxazolidin-2-ones is described. The reaction of allyl (aryl/alkyl) carbamates with fluoroalkyl iodide initiated by sodium dithionite in aqueous acetonitrile resulted in adducts that undergoes a cyclization assisted by microwave irradiation to form 5-fluoroalkyl-3-(aryl/alkyl)-oxazolidin-2-ones with high yields. It was also found that the products can be more efficiently formed via an AIBN-initiated one-pot addition–cyclization sequence from benzyl allyl(aryl/alkyl) carbamates and fluoroalkyl iodide.

Diastereoselective Intramolecular Allyl Transfer from Allyl Carbamate Accompanied by 5‐endo‐trig Ring Closure

To All(oc) involved: A palladium-catalyzed formal 5-endo-trig heteroannulation of enones generated in situ from amino acid derived β-keto nitriles has been realized (see scheme; Alloc=allyl carbamate). The reaction proceeds with allyl-group transfer from the carbamate protecting group to generate two new contiguous stereocenters, including one quaternary center, with high selectivity.

Diastereoselective Intramolecular Allyl Transfer from Allyl Carbamate Accompanied by 5‐endo‐trig Ring Closure

Diastereoselective Intramolecular Allyl Transfer from Allyl Carbamate Accompanied by 5‐<i>endo</i>‐trig Ring Closure

ChemInform Abstract: Synthesis of Enantioenriched Tertiary Boronic Esters from Secondary Allylic Carbamates. Application to the Synthesis of C30 Botryococcene.

AbstractThe reaction of lithiated allylic carbamates with boronic esters proceeds with excellent α‐selectivity and retention of stereochemistry.

Correction to Synthesis of Enantioenriched Tertiary Boronic Esters from Secondary Allylic Carbamates. Application to the Synthesis of C30 Botryococcene

ADVERTISEMENT RETURN TO ISSUEPREVAddition/CorrectionORIGINAL ARTICLEThis notice is a correctionCorrection to Synthesis of Enantioenriched Tertiary Boronic Esters from Secondary Allylic Carbamates. Application to the Synthesis of C30 BotryococceneAlexander P. Pulis and Varinder K. Aggarwal*Cite this: J. Am. Chem. Soc. 2012, 134, 27, 11298Publication Date (Web):June 26, 2012Publication History Published online26 June 2012Published inissue 11 July 2012https://doi.org/10.1021/ja304872jCopyright © 2012 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views2667Altmetric-Citations2LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (120 KB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information Get e-Alerts