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1.
A convenient synthis for 4‐substituted and 3,4‐disubstituted 1,7‐naphthyridine‐2(1H)‐thiones 7 has been developed. The method is based on the electrocyclic reaction of 4‐(1‐arylalk‐1‐enyl)‐3‐isothiocyanatopyridines 6 , generated in situ by the treatment of the respective isocyanides 5 with S8 in the presence of a catalytic amount of selenium. The isocyanides 5 can be easily prepared from commercially available pyridin‐3‐amine by conventional organic reactions.  相似文献   

2.
The novel coumarin‐3‐carboxamides (=2‐oxo‐2H‐1‐benzopyran‐3‐carboxamides) 5a – 5g containing lipophilic spacers were synthesized through the Ugi‐four‐component reaction (Scheme 1). The reactions of aromatic aldehydes 1 , 4,4′‐oxybis[benzenamine] or 4,4′‐methylenebis[benzenamine] as diamine 2 , coumarin‐3‐carboxylic acid (=2‐oxo‐2H‐benzopyran‐3‐carboxylic acid; 3 ), and alkyl isocyanides 4 lead to the desired substituted coumarin‐3‐carboxamides 5a – 5g at room temperature with high bond‐forming efficiency. These novel coumarin derivatives exhibit brilliant fluorescence at 544 nm in CHCl3.  相似文献   

3.
Reaction of substituted o‐aminobenzyl chlorides with isocyanides in the presence of a weak base (NaHCO3) at room temperature afforded the diversely functionalized 2‐aminoindoles in good to excellent yields. A formal [4+1] cycloaddition of the in situ generated aza‐ortho‐xylylenes with isocyanides accounted for the reaction outcome.  相似文献   

4.
Both E‐ and ZN′‐alkenyl urea derivatives of imidazolidinones may be formed selectively from enantiopure α‐amino acids. Generation of their enolate derivatives in the presence of K+ and [18]crown‐6 induces intramolecular migration of the alkenyl group from N′ to Cα with retention of double bond geometry. DFT calculations indicate a partially concerted substitution mechanism. Hydrolysis of the enantiopure products under acid conditions reveals quaternary α‐alkenyl amino acids with stereodivergent control of both absolute configuration and double bond geometry.  相似文献   

5.
α‐Amino nitriles tethered to alkenes through a urea linkage undergo intramolecular C‐alkenylation on treatment with base by attack of the lithionitrile derivatives on the N′‐alkenyl group. A geometry‐retentive alkene shift affords stereospecifically the E or Z isomer of the 5‐alkenyl‐4‐iminohydantoin products from the corresponding starting E ‐ or Z N ′‐alkenyl urea, each of which may be formed from the same N ‐allyl precursor by stereodivergent alkene isomerization. The reaction, formally a nucleophilic substitution at an sp2 carbon atom, allows the direct regioselective incorporation of mono‐, di‐, tri‐, and tetrasubstituted olefins at the α‐carbon of amino acid derivatives. The initially formed 5‐alkenyl iminohydantoins may be hydrolyzed and oxidatively deprotected to yield hydantoins and unsaturated α‐quaternary amino acids.  相似文献   

6.
An efficient multicomponent reaction of 3‐indolyl‐3‐oxopropanenitriles with dialkyl acetylenedicarboxylates and isocyanides under mild conditions leading to highly functionalized 6‐(indol‐3‐yl)‐4H‐pyrans in moderate to good yields has been developed.  相似文献   

7.
The regioselective formation of (E)‐β‐vinylstannanes has been a long‐standing challenge in transition‐metal‐catalyzed alkyne hydrostannation. Herein, we report a well‐defined molybdenum‐based system featuring two encumbering m‐terphenyl isocyanides that reliably and efficiently delivers (E)‐β‐vinylstannanes from a range of terminal and internal alkynes with high regioselectivity. The system is particularly effective for aryl alkynes and can discriminate between alkyl chains of low steric hindrance in unsymmetrically substituted dialkyl alkynes. Catalytic hydrostannation with this system is also characterized by an electronic effect that leads to a decrease in regioselectivity when electron‐withdrawing groups are present on the alkyne substrate.  相似文献   

8.
The theoretical background of the formation of N‐heterocyclic oxadiazoline carbenes through a metal‐assisted [2+3]‐dipolar cycloaddition (CA) reaction of nitrones R1CH?N(R2)O to isocyanides C?NR and the decomposition of these carbenes to imines R1CH?NR2 and isocyanates O?C?NR is discussed. Furthermore, the reaction mechanisms and factors that govern these processes are analyzed in detail. In the absence of a metal, oxadiazoline carbenes should not be accessible due to the high activation energy of their formation and their low thermodynamic stability. The most efficient promotors that could assist the synthesis of these species should be “carbenophilic” metals that form a strong bond with the oxadiazoline heterocycle, but without significant involvement of π‐back donation, namely, AuI, AuIII, PtII, PtIV, ReV, and PdII metal centers. These metals, on the one hand, significantly facilitate the coupling of nitrones with isocyanides and, on the other hand, stabilize the derived carbene heterocycles toward decomposition. The energy of the LUMOCNR and the charge on the N atom of the C?N group are principal factors that control the cycloaddition of nitrones to isocyanides. The alkyl‐substituted nitrones and isocyanides are predicted to be more active in the CA reaction than the aryl‐substituted species, and the N,N,C‐alkyloxadiazolines are more stable toward decomposition relative to the aryl derivatives.  相似文献   

9.
Treatment of α,β‐unsaturated ketones with an electrophilic site at the γ‐position in the presence of trimethylsilyl cyanide with bis(iodozincio)methane afforded the (Z)‐silyl enol ether of the β‐cyclopropyl substituted ketone in good yields. The reaction proceeds by 1,4‐addition to form an enolate, and its sequential intramolecular nucleophilic attack to an adjacent electrophilic site. The reaction of γ‐ethoxycarbonyl‐α,β‐unsaturated ketone and bis(iodozincio)methane in the presence of trimethylsilyl cyanide afforded 1‐ethoxy‐1‐trimethylsiloxycyclopropane derivatives, which can be regarded as the homoenolate equivalent. Additionally, reaction of the obtained homoenolate equivalents with imines give 1‐(E)‐alkenyl‐2‐(1‐aminoalkyl)alkanols diastereoselectively.  相似文献   

10.
3‐(ω′‐Alkenyl)‐substituted 5,6‐dihydro‐1H‐pyridin‐2‐ones 2 – 4 were prepared as photocycloaddition precursors either by cross‐coupling from 3‐iodo‐5,6‐dihydro‐1H‐pyridin‐2‐one ( 8 ) or—more favorably—from the corresponding α‐(ω′‐alkenyl)‐substituted δ‐valerolactams 9 – 11 by a selenylation/elimination sequence (56–62 % overall yield). 3‐(ω′‐Alkenyloxy)‐substituted 5,6‐dihydro‐1H‐pyridin‐2‐ones 5 and 6 were accessible in 43 and 37 % overall yield from 3‐diazopiperidin‐2‐one ( 15 ) by an α,α‐chloroselenylation reaction at the 3‐position followed by nucleophilic displacement of a chloride ion with an ω‐alkenolate and oxidative elimination of selenoxide. Upon irradiation at λ=254 nm, the precursor compounds underwent a clean intramolecular [2+2] photocycloaddition reaction. Substrates 2 and 5 , tethered by a two‐atom chain, exclusively delivered the respective crossed products 19 and 20 , and substrates 3 , 5 , and 6 , tethered by longer chains, gave the straight products 21 – 23 . The completely regio‐ and diastereoselective photocycloaddition reactions proceeded in 63–83 % yield. Irradiation in the presence of the chiral templates (?)‐ 1 and (+)‐ 31 at ?75 °C in toluene rendered the reactions enantioselective with selectivities varying between 40 and 85 % ee. Truncated template rac‐ 31 was prepared as a noranalogue of the well‐established template 1 in eight steps and 56 % yield from the Kemp triacid ( 24 ). Subsequent resolution delivered the enantiomerically pure templates (?)‐ 31 and (+)‐ 31 . The outcome of the reactions is compared to the results achieved with 4‐substituted 5,6‐dihydro‐1H‐pyridin‐2‐ones and quinolones.  相似文献   

11.
A method for catalytic regio‐ and enantioselective synthesis of trifluoromethyl‐substituted and aryl‐, heteroaryl‐, alkenyl‐, and alkynyl‐substituted homoallylic α‐tertiary NH2‐amines is introduced. Easy‐to‐synthesize and robust N‐silyl ketimines are converted to NH‐ketimines in situ, which then react with a Z‐allyl boronate. Transformations are promoted by a readily accessible l ‐threonine‐derived aminophenol‐based boryl catalyst, affording the desired products in up to 91 % yield, >98:2 α:γ selectivity, >98:2 Z:E selectivity, and >99:1 enantiomeric ratio. A commercially available aminophenol may be used, and allyl boronates, which may contain an alkyl‐, a chloro‐, or a bromo‐substituted Z‐alkene, can either be purchased or prepared by catalytic stereoretentive cross‐metathesis. What is more, Z‐trisubstituted allyl boronates may be used. Various chemo‐, regio‐, and diastereoselective transformations of the α‐tertiary homoallylic NH2‐amine products highlight the utility of the approach; this includes diastereo‐ and regioselective epoxide formation/trichloroacetic acid cleavage to generate differentiated diol derivatives.  相似文献   

12.
The present study provides an efficient strategy for the preparation of novel N‐substituted‐4‐methyl‐quinolin‐1(2H)‐one derivatives via two‐step Ugi/Heck reaction. The procedure is based on the Ugi coupling between 2‐bromoanilines, various aromatic aldehydes, vinylacetic acid, and isocyanides, and then intramolecular Heck reaction, which leads to the formation of the title compounds in good yields.  相似文献   

13.
An efficient synthesis of functionalized tertiary α‐silyl alcohols by an enantio‐ and diastereoselective copper‐catalyzed three‐component coupling of 1,3‐dienes, bis(pinacolato)diboron, and acylsilanes is reported. The reaction proceeds well with different 1,3‐dienes and a broad range of aryl‐ as well as alkenyl‐ but also alkyl‐substituted acylsilanes. The target compounds are formed with high regio‐, diastereo‐, and enantioselectivity (up to 99 % ee and d.r. >20:1) and are highly versatile synthetic building blocks.  相似文献   

14.
We have developed an effective organometallic‐based procedure allowing the employment of 2‐methylphenols as easily available starting materials in the synthesis of 3‐alkylbenzofuran‐2(3H)‐ones. The first step of this protocol, an anionic homologous Fries‐rearrangement, afforded 2‐(2‐ tert ‐butyldimethylsilyloxyaryl)acetamides, which were selectively metalated and monoalkylated at the benzylic position. Acidic work‐up of crude products afforded the desired heterocycles in satisfactory overall yields. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

15.
Pteridines substituted with a 1,1‐, 1,2‐, or 1,1,3‐substituted alkenyl group (mostly (E)‐configured) at C(6) were synthesized in high yields by the intramolecular nitroso‐ene reaction of 4‐(alkenoylamino)‐2‐amino‐6‐benzyloxy‐5‐nitroso‐ and 4‐(alkenoylamino)‐2,6‐diamino‐5‐nitrosopyrimidines. Thus, the N‐alkenoyl nitrosopyrimidines 4 and 5 provided the pteridines 6 and 7 , respectively, characterized by a 1,2‐disubstituted (E)‐alkenyl substituent, the C(4)‐(E)‐geranoyl amide 13 led regio‐ and stereoselectively to the (E)‐1,1,2‐trisubstituted alkenyl‐pteridine 16 , and the C(4)‐(Z) isomer 14 led to 17 possessing a 1,1‐disubstituted alkenyl group. The trifluoromethylated butenoyl amide 15 possessing a less highly nucleophilic alkenoyl group reacted more slowly to give the trifluoromethylated vinylpteridine 18 . Also the 4‐(alkenoylamino)‐2,6‐diamino‐5‐nitrosopyrimidine 20 reacted more slowly than 4 and 5 , and provided the pteridines 23 ; introduction of additional N‐acyl groups as in 21 and 22 led to a considerably faster ene reaction. The X‐ray crystal structure analysis of the nitroso amide 15 shows eight symmetrically independent molecules in the unit cell. In the crystalline state, the N,N‐dimethylformamidine derivative 9 of 6 forms a centrosymmetric dimer with the 7,8‐lactam group connected by intermolecular hydrogen bonds.  相似文献   

16.
β‐Substituted chiral γ‐aminobutyric acids feature important biological activities and are valuable intermediates for the synthesis of pharmaceuticals. Herein, an efficient catalytic enantioselective approach for the synthesis of β‐substituted γ‐aminobutyric acid derivatives through visible‐light‐induced photocatalyst‐free asymmetric radical conjugate additions is reported. Various β‐substituted γ‐aminobutyric acid analogues, including previously inaccessible derivatives containing fluorinated quaternary stereocenters, were obtained in good yields (42–89 %) and with excellent enantioselectivity (90–97 % ee). Synthetically valuable applications were demonstrated by providing straightforward synthetic access to the pharmaceuticals or related bioactive compounds (S)‐pregabalin, (R)‐baclofen, (R)‐rolipram, and (S)‐nebracetam.  相似文献   

17.
On irradiation (254 nm), the newly synthesized Boc‐protected 5‐alkenyl‐2,5‐dihydro‐1H‐pyrrol‐2‐ones 13 undergo regioselective intramolecular [2+2] photocycloadditions. While the allyl derivatives 13a – 13c afford mainly azatricyclo[3.3.0.02,7]octanones, i.e., crossed cycloadducts, the butenyl‐ and pentenyl‐substituted compounds 13d and 13e isomerize preferentially to straight cycloadducts.  相似文献   

18.
In a limited number of cases, 14‐alkenylcodeinones (=14‐alkenyl‐7,8‐didehydro‐4,5‐epoxy‐3‐methoxy‐17‐methylmorphinan‐6‐ones) can be obtained by formic acid treatment of thevinols (=4,5‐epoxy‐3,6‐dimethoxy‐α,17‐dimethyl‐6,14‐ethenomorphinan‐7‐methanols), but under these conditions the equivalent 14‐alkenyl‐7,8‐dihydrocodeinones undergo further rearrangement (Scheme 1 and Table). Introduction of a 5β‐methyl group allows the 18,19‐dihydrothevinol precursors to be rearranged to 14‐alkenyl‐7,8‐dihydrocodeinones, but similar manipulation of the vinylogues of these thevinols is generally unable to prevent full rearrangement to 5,14‐bridged thebainone derivatives.  相似文献   

19.
β‐Bromo‐α,β‐unsaturated ketones are condensed with arylhydrazines to form hydrazones, which are in situ intramolecularly cyclized into 3‐substituted 1‐aryl‐1 H‐pyrazoles under a catalytic system of Pd(OAc)2/1,3‐bis(diphenylhosphino)propane (dppp)/NaOtBu. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

20.
The title compounds, the P(3)‐axially and P(3)‐equatorially substituted cis‐ and trans‐configured 8‐benzyl‐3‐fluoro‐2,4‐dioxa‐8‐aza‐3‐phosphadecalin 3‐oxides (=8‐benzyl‐3‐fluoro‐2,4‐dioxa‐8‐aza‐3‐phosphabicyclo[4.4.0]decane 3‐oxides=2‐fluorohexahydro‐6‐(phenylmethyl)‐4H‐1,3,2‐dioxaphosphorino[5,4‐c]pyridine 2‐oxides) were prepared (ee>98%) and fully characterized (Schemes 2 and 3). The absolute configurations were established from that of their precursors, the enantiomerically pure cis‐ and trans‐1‐benzyl‐4‐hydroxypiperidine‐3‐methanols which were unambiguously assigned. Being configuratively fixed and conformationally constrained phosphorus analogues of acetyl γ‐homocholine (=3‐(acetyloxy)‐N,N,N‐trimethylpropan‐1‐aminium), they are suitable probes for the investigation of molecular interactions with acetylcholinesterase. As determined by kinetic methods, all of the compounds are weak inhibitors of the enzyme.  相似文献   

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