Copper-catalyzed aerobic oxidative intramolecular alkene C-H amination leading to N-heterocycles

A copper-catalyzed aerobic oxidative intramolecular alkene C-H amination has been developed using readily available substituted 3-benzylidene-2-pyridin-2-ylmethyl-2,3-dihydro-isoindol-1-ones as the starting materials, and the corresponding N-heterocycles were obtained in good to excellent yields. This method should provide a new and useful strategy for constructing N-heterocycles.     

A [4 + 4] 2-pyridone approach to taxol. 3. Stereocontrol during elaboration of the cyclooctane

Intramolecular photocycloaddition of 2-pyridones connected through a four-carbon tether (6-[4-(1,2-dihydro-1-methyl-2-oxo-3-pyridinyl)-4-[[(1,1-dimethylethyl)++ +dimethylsilyl]oxy]butyl]-4-methoxy-1,3-dimethyl-2(1H)-pyridinone) yields a single tetracyclic product with four new stereogenic centers. The diastereoselectivity of this [4 + 4] reaction is fully controlled by a stereogenic carbon of the tether. Treatment of the photoproduct with osmium tetraoxide transforms the alkene to a diol and the enol ether to an alpha-hydroxy ketone, with stereocontrol dictated by nearby lactams that block one face of each alkene. Allylmagnesium bromide addition to the ketone also yields a single diastereomer, but unexpectedly this product results from approach of the nucleophile to the most-hindered face of the ketone. Study of this reaction in a model system has found the allylic nucleophile to be unique, with nonallylic reagents approaching along the expected, least-hindered path. This contrasteric addition likely results from coordination of the allylic nucleophile to the nearby amide. The amide can therefore act either as a steric shield or as a directing group. The three steps of photocycloaddition, cis-hydroxylation, and nucleophilic addition constructs both quaternary carbons of the cyclooctane and four of the five stereogenic centers found in the eight-membered ring of Taxol.     

Chemistry of 2-Methylene-2,3-dihydrofuran-3-ones: XVIII. Reaction of Oxalyl Chloride with Acetophenone and Dibenzoylmethane

Treatment of acetophenone and dibenzoylmethane with excess oxalyl chloride gave heterocyclization products, 2-(3-oxo-5-phenyl-2,3-dihydrofuran-2-ylidene)-5-phenyl-2,3-dihydrofuran-3-one and a mixture of 4-benzoyl-5-phenyl-2,3-dihydrofuran-2,3-dione with 4-benzoyl-2-dibenzoylmethylene-5-phenyl-2,3-dihydrofuran-3-one.     

Photocycloaddition of Cyclohex-2-enones to Tetramethoxyethylene: Formation of 2,2,3,3-Tetramethoxy-1-oxaspiro[3.5]non-5-enes

Cyclohex-2-enones 1a–1c undergo photocycloaddition to tetramethoxyethylene in benzene to afford 1-oxa-spiro[3.5]non-5-enes 3 in very good yields. In MeCN as solvent, higher relative amounts of bicyclo[4.2.0]octan-2-ones 4 are formed. Results from similar experiments with the same enones and 2,3-dimethylbut-2-ene or 1,1-dimethoxyethene indicate that the driving force for oxetane formation is a sufficiently large difference in redox potentials between E_red of the enone and E_ox of the alkene. A mechanism is proposed for cycloalk-2-enone + alkene photocycloadditions wherein the cyclobutane adducts arise from an exciplex intermediate and the oxetanes from a subsequently formed contact ion-pair.     

Proton affinities of ketones, vicinal diketones and α-keto esters: a computational study

The proton affinities of seven different ketones, vicinal diketones, and α-keto esters (acetophenone, 2,2,2-trifluoroacetophenone, 2,3-butanedione, 1-phenyl-1,2-propanedione, methyl pyruvate, ethyl benzoylformate, and ketopantolactone) have been evaluated theoretically using the conventional ab initio HF and several post-HF methods (MP2, MP4, CCSD), density functional methods with the B3LYP hybrid functional, as well as some ab initio model chemistries [CBS-4M, G2(MP2), and G3(MP2)//B3LYP]. The chemical compounds studied are frequently used substrates in the asymmetric hydrogenation over chirally modified platinum catalysts where the protonation properties of the chiral modifier and the substrates are of great interest. In most cases, the proton affinities (PAs) evaluated with the CCSD/6-311+G(d,p)//B3LYP/TZVP and G2(MP2) methods are in good agreement with the existing experimental ones. However, the previously reported PA of 2,3-butanedione seems to be too high by 10-15 kJ mol⁻¹. The B3LYP/TZVP//B3LYP/TZVP and MP2/6-311+G(d,p)//B3LYP/TZVP model chemistries predict proton affinities that are systematically higher and lower than the experimental PAs, respectively. If proton affinities are evaluated as the average of the PAs calculated with these two theoretical methods a very good agreement with the experimental results is obtained. The mean absolute deviation (MAD) from experiment of this combination method for the PAs of 13 test molecules is 4.0 kJ mol⁻¹. For 9 molecules composed only of first-row atoms the MAD is 2.5 kJ mol⁻¹. The B3LYP/TZVP//B3LYP/TZVP and MP2/6-311+G(d,p)//B3LYP/TZVP methods provide significant savings in computational time and disk space compared to the CCSD/6-311+G(d,p)//B3LYP/TZVP and G2(MP2) models. Therefore, it is suggested that if no experimental or highly accurate theoretical data is available (due to computational cost), the proton affinities of similar compounds as investigated in this paper, can be evaluated with the combination method. For the studied molecules, this method gives the following PAs (in kJ mol⁻¹): 788 (2,3-butanedione, exptl 802); 798 (2,2,2-trifluoroacetophenone, exptl 799); 811 (ketopantolactone); 813 (methyl pyruvate); 825 (1-phenyl-1,2-propanedione); 862 (acetophenone, exptl 861); 865 (ethyl benzoylformate).     

Photocycloaddition of 2-Oxopyran-3-carbonitriles to 2,3-Dimethylbut-2-ene

On acetone-sensitized irradiation in the presence of 2,3-dimethylbut-2-ene, α-cyano-α,β-unsaturated δ-lactone 5 is converted both to cyclopentapyrans resulting from stepwise addition of the alkene to the olefinic C(β)- and the nitrile C-atom of triplet excited 5 , and cyclobutapyranes, i.e., [2+2] cycloadducts. Similarly, direct irradiation of 1-benzopyran-3-carbonitrile 6 in the presence of the same alkene affords cyclobutabenzopyran 13 and cyclopentabenzopyran 14 , the latter resulting from an upper excited triplet state of 6 .     

beta-Silylcarbenes from isolable diazosilanes.

Manganese dioxide oxidation of the hydrazone derivative of tert-butyldimethylsilyl acetophenone gave 2-tert-butyldimethylsilyl-1-phenyldiazoethane (17) an isolable diazocompound. Thermal and Rh(II)-catalyzed decomposition of diazosilane 17 in cyclohexane led to 1-tert-butyldimethylsilyl-1-phenylethylene (19) as the major product. The formation of alkene 19 presumably involves (tert-butyldimethylsilyl)methylphenylcarbene (21), which undergoes preferential 1,2-silyl migration as opposed to 1,2-hydrogen migration. Thermal decomposition of 17 in cyclohexane under oxygen gave substantial amounts of tert-butyldimethylsilyl acetophenone, presumably by reaction of the intermediate carbene with oxygen. Thermal decomposition of 17 in methanol led to alkene 19 and 2-tert-butyldimethylsilyl-1-methoxy-1-phenylethane (22) as major products, along with a significant amount of trans-1-tert-butyldimethylsilyl-2-phenylethylene (20). Kinetic studies indicate that these products are not derived from acid-catalyzed decomposition of the diazocompound 17. Formation of the methyl ether product 22 suggests the involvement of a beta-silyl carbocation intermediate, and solvent isotope effect studies indicate that this cation is at least partially derived from protonation of diazocompound 17 by neutral methanol. Photochemical decomposition of 17 in methanol produced the alkene 19 (97%) along with a small amount (2.4%) of the methyl ether 22. Capture of a photochemically generated carbene 21 by methanol is the proposed origin of this minor product. Geometry optimization of trimethylsilylmethylphenylcarbene (8) and carbene 21 at the HF/6-31G computational level led to a conformation consistent with a hyperconjugative interaction between the vacant p-orbital of these carbenes and the adjacent C-Si bond. Carbenes 8 and 21 are not energy minima at the B3LYP/6-31G level, where they rearrange to alkenes without barrier via silyl migration. These theoretical findings contrast with the proposed trapping of carbene 21 by methanol and oxygen.     

Rhodium(III)‐Catalyzed [3+2] Annulation of 5‐Aryl‐2,3‐dihydro‐1H‐pyrroles with Internal Alkynes through C(sp2)?H/Alkene Functionalization

This study describes a new rhodium(III)‐catalyzed [3+2] annulation of 5‐aryl‐2,3‐dihydro‐1H‐pyrroles with internal alkynes using a Cu(OAc)₂ oxidant for building a spirocyclic ring system, which includes the functionalization of an aryl C(sp²) H bond and addition/protonolysis of an alkene CC bond. This method is applicable to a wide range of 5‐aryl‐2,3‐dihydro‐1H‐pyrroles and internal alkynes, and results in the assembly of the spiro[indene‐1,2′‐pyrrolidine] architectures in good yields with excellent regioselectivities.     

新型N-P配体的合成、表征及其在氢转移反应中的应用

利用2,3-二(二苯膦氧基)-1,3-丁二烯与胺的迈克尔加成反应,合成了单胺基及环胺基改性的有机氧化膦,经有机硅烷还原,制备出胺基取代的膦配体,所得化合物经NMR及单晶X射线衍射分析.考察了所得配体与Ru(PPh3)3Cl2组成的催化体系在苯乙酮氧转移反应中的催化活性,发现氧化膦与Ru原位形成的催化剂比其还原态的三价膦组成的催化剂催化活性还高,二胺基取代的二氧化膦配体具有较高的催化活性,TON可达273.而采用先制备催化剂再催化反应时配体6的钌络合物催化活性TON可达352.     

Rhodium(III)‐Catalyzed [3+2] Annulation of 5‐Aryl‐2,3‐dihydro‐1H‐pyrroles with Internal Alkynes through C(sp2)H/Alkene Functionalization

This study describes a new rhodium(III)‐catalyzed [3+2] annulation of 5‐aryl‐2,3‐dihydro‐1H‐pyrroles with internal alkynes using a Cu(OAc)₂ oxidant for building a spirocyclic ring system, which includes the functionalization of an aryl C(sp²)? H bond and addition/protonolysis of an alkene C?C bond. This method is applicable to a wide range of 5‐aryl‐2,3‐dihydro‐1H‐pyrroles and internal alkynes, and results in the assembly of the spiro[indene‐1,2′‐pyrrolidine] architectures in good yields with excellent regioselectivities.     

Intramolecular 4+2 cycloaddition of thieno[2,3-e][1,2,4]triazines: routes towards condensed thieno[2,3-b]pyridines

Synthetic approaches towards new condensed thienopyridine ring systems including furo[2,3-b]thieno[3,2-e]pyridines, bisthieno[2,3-b:3′,2′-e]pyridines, 5H-chromeno[2,3-b]thieno[3,2-e]pyridines, 5H-benzo(f)chromeno[2,3-b]thieno[3,2-e]pyridines have been achieved by application of intramolecular 4+2 cycloaddition reactions of suitably designed thieno[2,3-e][1,2,4]triazines tethered with alkene or alkyne terminals.     

Synthesis and properties of azoles and their derivatives 35. Regioselectivity and stereoselectivity of the [2+3]-cycloaddition of phenyl nitrones to 1-decene

It was shown by spectroscopic methods that the [2+3]-cycloaddition of C,C,N-triphebyl nitrone to 1-decene is regiospecific and leads to 2,3,3-triphenyl-5-octylisoxazolidine as the only reaction product, whereas Z-C,N-diphenyl nitrone with the same alkene forms a mixture of stereoisomeric 2,3-iphenyl-5-octylisoxazolidines. The regiochemistry of the reaction was explained in terms of PMO theory.For Communication 34, see [1].Institut Chemii i Technologii Organiczney, Politechnika Krakowska im. Tadeusza Kosciuszki, 31–155 Krakow, Poland. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 373–377, March, 1998.     

Structure of the photoproduct from the cycloadduct of 2,3-diphenyl-2,3-epoxy-1-indanone and dibenzoylacetylene

A single crystal x-ray analysis of the photoproduct, from the cycloadduct (1) of 2,3-dipheny1–2,3-epoxy-1-indanone and dibenzoylacetylene, has shown that its structure is 3,3a-dibenzoyl-3a,8b-dihydro-2, 8b-diphenylindeno[l,2-b]furan-4-one (8a) and not the earlier reported benzoxocinone structure (3a). Reasonable pathways for the formation of 8a and analogous products are presented. Contribution No. NDRL-3312 and No. RRLT-PRU-10 from the Regional Research Laboratory, Trivandrum.     

Homogeneous asymmetric catalysis by means of chiral metal complexes of 2,3-bis(dimenthylphosphino)maleic anhydride and of 2,3-bis(dimenthylphosphino)maleimide derivatives

2,3-Bis(dimenthylphosphino)maleic anhydride and also 2,3-bis(dimenthylphosphino)maleimide derivatives have been prepared from 2,3-dichloromaleic anhydride, 2,3-dichloro-N-phenylmaleimide and 2,3-dichloro-N-methylmaleimide, respectively, and dimenthyl(trimethylsilyl)phosphine. These compounds have been used as ligands for Rh complexes in the asymmetric hydrogenation and hydrosilylation. Ni and Pd complexes of these ligands were tested in the Grignard cross-coupling reaction.

The hydrogenation of -acetamido cinnamic acid gave 70% enantiomeric excess (ee) and hydrogenation of acetophenone up to 47% ee. Hydrosilylation of acetophenone led to 42% ee.

Attempts to asymmetric cross-coupling reactions resulted in very low enantiomeric excess.     

Cycloaddition of Cyclopentadiene to 3-Deoxy-1,2:5,6-di-O-isopropylidene-alpha-D-erythro-hex-3-enofuranose. Synthesis and Representative Chemistry of 1,6-Anhydro-2,3-dideoxy-beta-D-glycero-hex-2-enopyran-4-ulose ("Isolevoglucosenone")

Treatment of D-glucose-derived alkene 4 with cyclopentadiene in the presence of a Lewis acid results in the formation of cycloaddition products 8-11. Evidence is presented to show that these 1,6-anhydro sugar-cyclopentadiene adducts do not arise from rearrangement of 4 to isolevoglucosenone (5) followed by cycloaddition but are the result of Lewis acid-catalyzed rearrangement of alkene 4 to acyclic dienophile 12 followed by addition of cyclopentadiene. Major cycloadduct 8 has been utilized as a source of the enantiomerically pure carbocycles 14-25 by manipulation of the alkene and ketone functions and cleavage of the 1,6-anhydro bridge. In the absence of diene, alkene 4 undergoes rearrangement to enone 5 in 32% yield. Reaction of 5 with several dienes results only in the formation of "bottom-face" adducts 10,11, 28, and 29, and conjugate addition of either HN(3) or Me(3)COOH is found to be completely stereoselective to afford 30 and 31, respectively. Subsequent manipulation of azide 30 leads to precursors of several naturally occurring 2-amino-2,3-dideoxy sugars.     

吲哚啉螺萘并吡喃的合成和时间分辩光谱研究

螺萘并吡喃类化合物是一类重要的有机光致变色化合物,因可用作光敏、光信息和光记录材料,而引起人们的研究兴趣．其中对螺苯并吡喃和螺嗪两类化合物的开环机理有较多的文献报道［１,２］,而对螺萘并吡喃的研究则少得多．我们合成了３个螺萘并吡喃化合物（其中ＳＰ１...     

Substantial (2)h-magnetic isotope effects on the diastereoselectivity of triplet photocycloaddition reactions

Magnetic isotope effects (MIE) on the diastereoselectivity of the triplet [2+2]-photocycloaddition of benzaldehyde with 2,3-dihydrofuran are described for four substrate combinations. The MIE results from H/D exchange at the reactive carbons of either the aldehyde or the alkene, respectively, but also from deuteration of the aromatic positions of benzaldehyde. Weaker isotope effects on the diastereoselectivity were detected for the reaction of alpha-deuterated propionaldehyde.     

A new pathway in the reaction of disilene with carbonyl compounds: an 'ene' reaction instead of cycloaddition

The 3H-disilagermirene, (tBu2MeSi)4GeSi2, reacts with alpha-hydrogen containing carbonyl compounds (acetophenone, butane-2,3-dione) by an 'ene'-reaction pathway followed by isomerization or insertion reactions, representing a new mode in the reaction of disilenes with carbonyl compounds.     

Chemistry of beta-functionalized alpha-nitroso ethylenes. Methyl beta-nitroso acrylate as heterodienophile in

[formula: see text] beta-Functionalized nitroso alkene 2, obtained from methyl beta-nitropropionate 1 and N,O-bis(trimethylsilyl)acetamide, can function as a good heterodienophile in Diels-Alder reactions. Therefore, 2 was trapped by cyclic dienes to give adducts 4 with the corresponding stereoselectivity. Cycloadduct 4a undergoes retro-[4 + 2]-cycloaddition at 33 degrees C in solution; thus 4a can be used to generate nitroso alkene 2 in neutral medium. Cyclopentadiene reacts with adduct 4a according to an endo-(4 + 2]-cycloaddition scheme to give cycloadduct 5 in low yield.