B-Substituted Carboranyl Thio- and Selenophosphites. Synthesis and Chemical Properties

Abstract

The first examples of B-substituted carboranyl thio- and selenoesters of trivalent phosphorus acids were synthesized. On the basis of these samples, a series of new corresponding pentavalent phosphorus acids derivatives, potentialy bioactive compounds, was obtained. S- and Se-carborane-9-yl-diethyl-thiophosphites (I) were obtained by the interaction of diethylchlorphosphites with 9-mercapto- or 9-selenocarboranes in the presence of triethylamine.     

Dihydroquinolines,Dihydronaphthyridines and Quinolones by Domino Reactions of Morita-Baylis-Hillman Acetates

An efficient synthetic route to highly substituted dihydroquinolines and dihydronaphthyridines has been developed using a domino reaction of Morita-Baylis-Hillman (MBH) acetates with primary aliphatic and aromatic amines in DMF at 50–90 °C. The MBH substrates incorporate a side chain acetate positioned adjacent to an acrylate or acrylonitrile aza-Michael acceptor as well as an aromatic ring activated toward S_NAr ring closure. A control experiment established that the initial reaction was an S_N2′-type displacement of the side chain acetate by the amine to generate the alkene product with the added nitrogen nucleophile positioned trans to the S_NAr aromatic ring acceptor. Thus, equilibration of the initial alkene geometry is required prior to cyclization. A further double bond migration was observed for several reactions targeting dihydronaphthyridines from substrates with a side chain acrylonitrile moiety. MBH acetates incorporating a 2,5-difluorophenyl moiety were found to have dual reactivity in these annulations. In the absence of O₂, the expected dihydroquinolines were formed, while in the presence of O₂, quinolones were produced. All of the products were isolated in good to excellent yields (72–93%). Numerous cases (42) are reported, and mechanisms are discussed.     

四甲基吡嗪多元醇及其乙酸酯的合成

四甲基吡嗪经溴代和酯化反应得到2,3,5-三乙酰氧甲基-6-甲基吡嗪(4)和2,3,5,6-四乙酰氧甲基吡嗪(5);4和5分别经水解得2,3,5-三羟甲基-6-甲基吡嗪和2,3,5,6-四羟甲基吡嗪。其结构经UV,1H NMR,13C NMR,IR和MS表征。     

Synthesis of 2-Acetamido-5,6-dihalophenyl Acetates

Summary.  2-Acetamido-5,6-dihalophenyl acetates were synthesized as intermediates for the preparation of 6, 7-dihalo-8-quinolinols via the Skraup procedure. Received January 24, 2000. Accepted February 12, 2000     

Triton-B-Catalyzed,Efficient, One-Pot Synthesis of Dithiocarbazates Through Alcoholic Tosylates

A quick, efficient, one-pot synthesis of dithiocarbazates was accomplished in high yields by the reaction of various tosylates of primary, secondary, and tertiary alcohols with a variety of substituted hydrazines using the benzyl–trimethylammonium hydroxide (Triton-B)/CS₂ system. The reaction conditions are mild with simpler workup procedures than the reported methods.     

Triton-B Catalyzed, Efficient, One-Pot Synthesis of Carbamate Esters from Alcoholic Tosylates

A novel process for the one-step chemoselective conversion of a variety of alcoholic tosylates into carbamates serving as protected amines was developed using benzyltrimethylammonium hydroxide (Triton-B) in the presence of gaseous carbon dioxide. Thus carbamate esters of different amines were prepared in very good to excellent yields.     

Triton-B-Catalyzed,Efficient, One-Pot Synthesis of Carbazates Through Alcoholic Tosylates

A quick, efficient, one-pot synthesis of carbazates was accomplished in high yields by the reaction of various tosylates of primary, secondary, and tert alcohols, with a variety of substituted hydrazines using the benzyltrimethylammonium hydroxide (Triton-B)/CO₂ system. The reaction conditions are mild with simpler workup procedures than the reported methods.     

A One-Step Conversion of Certain Indole and Pyrrole Glyoxtlic Acid Esters to the Corresponding Acetates

In this study, a catalytic hydrogen transfer type of hydrogenolysis was developed for the one step conversion of ethyl in-dole-3-, pyrrole-2- and pyrrole-3-glyoxalates to the corresponding acetates. The structural requirements for this hydrogenalysis were also investigated.     

Cyclization Reactions of Aryl Propargyl Acetates with Tethered Epoxide Induced by Ruthenium Complex

Reactions of the ruthenium complex [Ru]Cl ([Ru]=Cp(PPh₃)₂Ru; Cp=η⁵‐C₅H₅) with several aryl propargyl acetates, each with an ortho ‐substituted chain of various length containing an epoxide on the aromatic ring and with or without methyl substitutents on the epoxide ring, bring about novel cyclizations. The cyclization reactions of HC≡CCH(OAc)(C₆H₄)CH₂(RC₂H₂O) (R=H, 6 a ; R=CH₃, 6 b , where RC₂H₂O is an epoxide ring) in MeOH give the vinylidene complexes 5 a – b , respectively, each with the Cβ integrated into a tetrahydro‐5H ‐benzo[7]annulen‐6‐ol ring. A C−C bond formation takes place between the propargyl acetate and the less substituted carbon of the epoxide ring. Further cyclizations of 5 a – b induced by HBF₄ give the corresponding vinylidene complexes 8 a – b each with a new 8‐oxabicyclo‐[3.2.1]octane ring by removal of a methanol molecule in high yield. For similar aryl propargyl acetates with a shorter epoxide chain, the cyclization gives a mixture of a vinylidene complex with a tetrahydronaphthalen‐1‐ol ring and a carbene complex with a tricyclic indeno‐furan ring. For the cyclization of 18 , with a longer epoxide chain, opening of the epoxide is required to afford the vicinal bromohydrin 22 , then tandem cyclization occurs in one pot. Products are characterized by spectroscopic methods as well as by XRD analysis.     

Hypervalent Iodine in Synthesis XXV: An Effective Synthesis of Acetylenic Selenides via Alkynylphenyliodonium Tosylates

Acetylenic selenides have been prepared by the reaction of sodium are-neselenolates with alkynylphenyliodonium tosylates in DMF.     

Synthesis of Arylnaphthoquinones and Their Reactions with o‐Substituted Primary Aromatic Amines

Cycloaddition reaction of 2‐aryl‐1,4‐benzoquinones 1a‐d with a number of different dienes, namely 2,3‐dimethylbutadiene; 1,4‐diphenylbutadiene and anthracene yield 2‐aryl‐6,7‐dimethyl‐1,4‐ naphthoquinones 3a,b ; 2,5,8‐triphenyl‐1,4‐naphthoquinone 4 and 2‐aryl‐1,4,9,10‐tetrahydro‐9,10‐o‐benzoanthracene‐1,4‐dione 5 , respectively were investigated. In addition, the cycloaddition reaction of 2‐aryl‐1,4‐benzoquinones 1d,e with 2,3‐dimethylbutadiene was also investigated to yield 2‐aryl‐5,8‐dihydro‐6,7‐dimethyl‐1,4‐naphthohydroquinones 2a,b . Cyclocondensation reactions of Diels‐Alder adducts 2b, 3b, 5a with ethylenediamine, o‐substituted primary aromatic amines gave quinoxaline, phenazine, phenoxazine and phenothiazine ocyclic derivatives 6–14.     

An Efficient,Basic Resin-Mediated,One-Pot Synthesis of Dithiocarbazates Through Alcoholic Tosylates

A quick and efficient, one-pot synthesis of dithiocarbazates was accomplished in high yields by the reaction of various alcoholic tosylates of primary, secondary, and tertiary alcohols, with substituted hydrazines using an Amberlite IRA 400 (basic resin)/CS ₂ system. The reaction conditions are mild with simpler work-up procedures than previously reported methods.     

Cobalt‐Catalyzed Aminocarbonylation of Alkyl Tosylates: Stereospecific Synthesis of Amides

Metal‐catalyzed aminocarbonylation is a standard approach for installing amide functionality in chemical synthesis. Despite broad application of this transformation using aryl or vinyl electrophiles, there are few examples involving unactivated aliphatic substrates. Furthermore, there are no stereocontrolled aminocarbonylations of alkyl electrophiles known. Herein, we report a stereospecific aminocarbonylation of unactivated alkyl tosylates for the synthesis of enantioenriched amides. This cobalt‐catalyzed transformation uses a remarkably broad range of amines and proceeds with excellent stereospecificity and chemoselectivity.     

Triton-B Catalyzed, Efficient, One-Pot Synthesis of Carbamate Esters from Alcoholic Tosylates

Summary. A novel process for the one-step chemoselective conversion of a variety of alcoholic tosylates into carbamates serving as protected amines was developed using benzyltrimethylammonium hydroxide (Triton-B) in the presence of gaseous carbon dioxide. Thus carbamate esters of different amines were prepared in very good to excellent yields. Present address: Institute of Organic and Biomolecular Chemistry, Georg-August University, D-37077, G?ttingen, Germany     

Cu-Catalyzed Cascade Cyclization of Ketoxime Acetates and Alkynals Enabling Synthesis of Acylpyrroles

Main observation and conclusion A facile copper-based catalytic system has been developed to enable efficient cyclization of methylketoximes and alkynals.This p...     

Heterolytic Fragmentations of Malortyl Tosylates

Heterolytic fragmentation reactions have figured prominently in several recent multistep syntheses².,³ As part of an investigation of those reactions in which, at least formally, a stabilized carbanion serves as the electrofugal group²,⁴ we have examined a number of substituted malonic esters with the aim of effecting the following sequence: