摘要:

AbstractThe Rh(II)‐catalyzed intramolecular CH insertion reactions of N,N‐dialkyl‐α‐diazo‐α‐(diethylphosphono)acetamides2a,f–jin CHCl3or ClCH2CH2Cl were found to give monocyclic and bicyclic α‐phosphono‐β‐lactams,3aand3f–j, in 43–67% yields via regiospecific α‐CH insertion of the N‐alkyl groups. Similar treatment of N‐benzyl‐N‐isopropyl‐α‐diazo‐α‐(diethylphosphono)acetamide (2b) and the corresponding N‐isobutyl‐N‐methylacetamide2din ClCH2CH2Cl afforded mixtures of β‐lactams3b(35%) and and3b′ (16%), β‐lactam3d(47%), and γ‐lactam4d(10%), respectively, each of which is formed by the competitive CH insertion reaction between benzylic and isopropyl α‐CH bonds and between methyl α‐CH and methine β‐CH bonds, respectively. For the formation of β‐lactams, the selectivity in the rhodium‐mediated CH insertion in ClCH2CH2Cl follows the order methyl>methine>benzylic α‐CH bond on N‐substituents. The N,N‐dibutyl‐α‐diazo homologue2cand Nα[α‐diazo‐α‐(diethylphosphono)acetyl]‐2‐methylindoline (2k) exclusively produced γ‐lactams4c(67%) and4k(81%) via insertion into the methylene β‐CH and methyl β‐CH bonds. tert‐Butyl N‐[α‐diazo‐α‐(dibenzylphosphono)acetyl]‐piperidine‐2‐carboxylate (2m) on similar treatment, followed by deprotection of the benzyl ester afforded the 7‐phosphono carbacepham6in 32% overall yield. Similar Rh(II)‐catalyzed cyclization of N‐methyl‐N[4‐benzyloxy‐α‐(diethylphosphono)‐phenyl(diethyl‐phosphono)methyl]‐α‐diazo‐acetamide (2n) led to 1‐[4′‐benzylphenyl(diethylphosphono)methyl] ‐3‐(diethyl‐phosphono)azetidin‐2‐one (3n) in 78% yicld. The phosphono group at C‐7 of3fwas converted into the acetylamino group

ISSN:1042-7163    

DOI:10.1002/hc.520060304

出版商:VCH Publishers, Inc.    

年代:1995

数据来源: WILEY

摘要:

Abstractα‐(Thiocyanatomethyl)benzylidenemalononitrile undergoes bromination with N‐bromo succinimide to afford α‐(bromothiocyanatomethyl)benzylidenemalononitrile. This bromo derivative undergoes reactions with sodium hydrogen sulfide, thioglycollic acid, hydroxylamine hydrochloride, phenylhydrazine, and hydrazine hydrate to afford thiophene, 4H‐thiopyran, 4H‐oxazine, pyridazine, and bis(thiazol‐2‐ylidene)azine derivatives, respectively. Mechanistic explanations as well as structure elucidation

ISSN:1042-7163    

DOI:10.1002/hc.520060305

出版商:VCH Publishers, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractSodium2and potassium selenocarbamates3were found to be synthesized in moderate to good yields by the reaction of carbamoyl chlorides with sodium and potassium selenides. The salts2and3reacted with alkyl halides and organo‐germanium, ‐tin, and ‐lead chlorides to give the corresponding esters7–9in good

ISSN:1042-7163    

DOI:10.1002/hc.520060306

出版商:VCH Publishers, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractTrialkyl phosphites (1), dialkyl phenylphosphinites (2), and alkyl diphenylphosphonites (3) as well as 2‐phenyl‐1,3,2‐dioxaphospholan (4b) and 2‐phenyl‐1,3,2‐dioxaphosphorinan (4b) give rise to dediazoniation of arenediazonium salt (5) in an alcoholic solvent under an argon atmosphere at 20°C. The reaction proceeds via a radical‐chain mechanism initiated by single‐electron transfer (SET) from the trivalent‐phosphorus compounds to5, as a result of which, an aryl radical Ar⋅ and a cation radical15are generated from the former and the latter, respectively. The aryl radical Ar⋅ participates in this chain process abstracting a hydrogen from the solvent alcohol, yielding the corresponding arene ArH. The cation radical15undergoes both an ionic reaction with the solvent alcohol and a radical coupling with Ar⋅, giving the phosphoranyl radical16and the phosphonium ion17, respectively, as intermediates. The phosphoranyl intermediate16decomposes through either the SET process to5or by β‐scission, yielding the oxidation product (phosphate, phosphonate, or phosphinate from1,2, or3, respectively, or phosphonates from4). The phosphonium intermediate17affords the arylated product (phosphonate, phosphinate, or phosphine oxide from1,2,3, respectively, or the phosphinate from4). Among the trivalent‐phosphorus compounds tested,1gives the arylated product in the highest yield. This observation, together with the literature data of ESR for structurally related phosphoranyl radicals, indicates that the radical coupling of15with Ar⋅ is facilitated by the high spin density

ISSN:1042-7163    

DOI:10.1002/hc.520060307

出版商:VCH Publishers, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractReaction of Se‐Alkyl phosphinoselenoates with organometallics resulted in a selective attack on the selenium atom. Sequential treatment of optically active Se‐benzyl t‐butylphenylphosphinoselenoate with PhLi and then with electrophiles, such as alkyl halides, an α,β‐unsaturated ester, and chalcogen atoms gave optically active phosphorus compounds in 5–91% yields and in high optical yields, with retention of configuration at the phosphorus atom, along with a quantitative yield of benzyl phen

ISSN:1042-7163    

DOI:10.1002/hc.520060308

出版商:VCH Publishers, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractAromatic diselenoic acid Se‐methyl esters1react with amines at 0°C in tetrahydrofuran (THF) to yield selenoamides in moderate to good yields. The reaction course is highly dependent on the steric requirements of both starting materials. In the reactions of the ester1awith 2‐methylpiperidine and of the ester1bwith piperidine, the starting materials disappear within 1 hour with the liberation of black selenium, but the corresponding selenoamides are not produced. These results may be ascribed to the steric congestion caused by the formation of the selenoamide group from the tetrahedral intermediate15. X‐ray crystal structure analyses of the selenoamides3and9have been performed. The bond length of C(Se)N is shorter than a carbon nitrogen single bond. On the other hand, the CSe bond is longer than that of the ordinary carbon‐selenium double bond. These results are indicative of the efficient delocalization of the electrons of nitrogen to the carbon–selenium double bond. The double bond character between the carbon attached to selenium and the nitrogen is also supported by the nitrogen atom showing sp2character. When a methyl group is introduced at the meta position of the aromatic ring, the deviation of the aromatic ring from the plane involving the carbon–selenium double bond and nitrogen atom becomes substantially large, perhaps due to the steric bulkiness of t

ISSN:1042-7163    

DOI:10.1002/hc.520060309

出版商:VCH Publishers, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractAsymmetric trans‐addition reactions of simple olefins have been performed by using optically active 2‐selenobinaphthyls1,2a–g.Introduction of an amide group at the 2′‐position in the binaphthyl skeleton enhances considerably the diastereomeric excess (de) of the asymmetric methoxyselenenylation. In the case of trans‐olefins, introduction of another chiral center in the amide group further enhances the de due to double stereodifferentiation between the (R)‐binaphthyl skeleton and the chiral amide group introduced at the 2′‐position in the binaphthyl skeleton. The use of chiral nucleophiles is also effective to enhance the de for symmet

ISSN:1042-7163    

DOI:10.1002/hc.520060310

出版商:VCH Publishers, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractReactions of tris(methylsenleno)borane‐SnCl4with alkenes1a–ggave α,β‐bis(methylseleno)alkanes2a–g, stereospecifically, and reactions with 1,3‐dienes1i–kafforded α,β‐bis(methylseleno)alk‐2‐enes2

ISSN:1042-7163    

DOI:10.1002/hc.520060311

出版商:VCH Publishers, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractMetal and temperature effects on thio‐Wittig reactions have been studied. Stabilized phosphorus ylides, such as carbomethoxymethylenetriphenylphosphorane, reacted with sulfur to afford dimethyl maleate and dimethyl fumarate in a 1:4 ratio. As in the case of conventional Wittig reactions with semistabilized ylides, it has been shown that the stereochemistry (E:Z ratio) of alkene formation is determined at the point that a new carbon–carbon bond has been formed to give a thiaphosphetane intermediate. The temperature dependence of this reaction is also discus

ISSN:1042-7163    

DOI:10.1002/hc.520060312

出版商:VCH Publishers, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractSeveral types of addition reactions to the CC bond of alkyl 2‐cyanoacrylates, CH2C(CN)COOR (1), are considered. The first examples deal with addition of CH‐Acids (pKaless than 13) and of H2S in the presence of catalytic amounts of strong amines, also of mercaptans, thiocarboxylic, and thiophosphoric acids. P‐Sulfenylchlorides and acidic phosphites add irreversibly at 20°C to form addition products in accordance with the distribution of charges in1. HCl reversibly adds to1and to the acid chloride CH2C(CN)COCl (2). Alcohols and H2O also add reversibly to the acid CH2C(CN)COOH (3) and to esters of1to transform1and3into polymers. Triethylsilane in the presence of CF3COOH (4) reduces the CC bond of1and3to the corresponding saturated derivatives.The second set of examples involves reactions of1with P‐III compounds in the presence or absence of4. Ph3P as well as other weak nucleophiles reversibly add to1in the absence of4to cause instant polymerization. However,4protonates an initially formed zwitter‐ion in the reaction of1with Ph3P,(EtO)2PCl,Ph2PCl and thiourea to afford stable addition products.IRspectroscopy reveals the formation of H‐complexes of4with the CN and COOR groups of1, which stimulates the addition of the weak nucleophile (o‐C6H4O2)PCl to the CC bond of1. This reagent does not react with1in the absence of4. Strong nucleophiles, Alk3P, and (Et2N)3P in excess irreversibly add at 20°C to1to form zwitterions, which specifically react with PhNCO to give stable products. 1,3,2‐Dioxaphospholes react with1either to form spirophosphoranes or

ISSN:1042-7163    

DOI:10.1002/hc.520060313

出版商:VCH Publishers, Inc.    

年代:1995

数据来源: WILEY