Introducing Deep Eutectic Solvents to Polar Organometallic Chemistry: Chemoselective Addition of Organolithium and Grignard Reagents to Ketones in Air

Despite their enormous synthetic relevance, the use of polar organolithium and Grignard reagents is greatly limited by their requirements of low temperatures in order to control their reactivity as well as the need of dry organic solvents and inert atmosphere protocols to avoid their fast decomposition. Breaking new ground on the applications of these commodity organometallics in synthesis under more environmentally friendly conditions, this work introduces deep eutetic solvents (DESs) as a green alternative media to carry out chemoselective additions of ketones in air at room temperature. Comparing their reactivities in DES with those observed in pure water suggest that a kinetic activation of the alkylating reagents is taking place, favoring nucleophilic addition over the competitive hydrolysis, which can be rationalized through formation of halide‐rich magnesiate or lithiate species.     

Synthesis and Crystal Structure of 3-Ethoxycarbonyl-4,6-diphenyl-3,4-dihydropyridine-2(1H)-thione

3-Ethoxycarbonyl-4,6-diphenyl-3,4-dihydropyridine-2(1H)-thione was synthesized by the interaction of benzylideneacetophenone with cyanoacetic ester and hydrogen sulfide. Its structure was investigated by X-ray structural analysis. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1180–1183, August, 2005.     

Facile one-pot three-component synthesis of 4,6-diaryl-3,4-dihydropyrimidine-2(1H)-thiones under ultrasonic irradiation

Abstract

We developed a facile one-pot procedure for the synthesis of 4,6-diaryl-3,4-dihydropyrimidine-2(1H)-thione under ultrasonic irradiation. The method is based on a three components reaction of aldehydes, ketones, and thiourea under basic conditions affording isolated yields of up to 95% within a reaction time of 30–90?min.     

Very Simple One-Step Synthesis of Vinylphosphonates and Enamine Phosphonates by Direct Addition of Organolithium Reagents to 1-Alkynylphosphonates

Abstract

Direct addition of organolithium to 1-alkynylphosphonates (1) afforded vinylphosphonates and enamine phosphonates (2) in good to excellent yields. The reaction was carried out in dry THF at low temperature and proved to be completely stereoselective (syn addition). Alkyl, aryl, and haloalkyl groups were attached to the alkynyl entity, so the resulting vinylphosphonates contained various functional groups. The stereochemistry of the products as well as mechanism of the reaction were determined based on ¹H and ¹³C NMR. The synthesis of enamine phosphonates in the absence of complicated, highly expensive organometallic catalysis has not been previously reported.     

One-Pot Syntheses of 3,4-Dihydropyrimidine-2(1H)-thiones Catalyzed by La(OTf)_3

ＩｎｔｒｏｄｕｃｔｉｏｎＩｎｒｅｃｅｎｔｙｅａｒｓ ,ｄｉｈｙｄｒｏｐｙｒｉｍｉｄｉｎｅｔｈｉｏｎｅｄｅｒｉｖａｔｉｖｅｓｈａｖｅａｔｔｒａｃｔｅｄｃｏｎｓｉｄｅｒａｂｌｅｉｎｔｅｒｅｓｔｄｕｅｔｏｔｈｅｉｒｐｒｏｍｉｓｉｎｇａｃｔｉｖｉｔｉｅｓａｓａｎｔｉｃａｒｃｉｎｏｇｅｎｉｃａｇｅｎｔｓ ,1ｃａｒｄｉｏｖａｓｃｕｌａｒａ ｇｅｎｔｓ2 ａｎｄｃａｌｃｉｕｍｃｈａｎｎｅｌｂｌｏｃｋｅｒｓ .3Ｉｎａｄｄｉｔｉｏｎ ,ｓｏｍｅｄｅｒｉｖａｔｉｖｅｓｏｆｄｉｈｙｄｒｏｐｙｒｉｍｉｄｉｎｅｔｈｉｏｎｅｗｅｒ…     

1-烷基-4,6-二芳基四氢三嗪硫酮化合物的合成及其氧化反应

三芳基缩二胺与烷基硫脲在二氧六环回流条件下反应, 可生成1-烷基-4,6-二芳基四氢三嗪硫酮化合物3。利用芳香醛, 烷基硫脲和醋酸铵一锅法也能得到3, 而三芳基缩二胺与芳基硫脲反应, 则生成了咪唑啉的硫氰酸盐。室温下,在相转移催化剂TEBA存在时, 3可被高锰酸钾氧化, 得到1-烷基-4,6-二芳基-2(1H)三嗪酮化合物。     

Elektrophile Substitution und nucleophile Addition an 3,4-Dihydro-5(1H)-pyrromethenonen

3,4-Dihydro-5(1H)-pyrromethenones are easier attacked at themeso-position by electrophiles than 5(1H)-pyrromethenones. This is demonstrated both by aMannich-type-substitution or deuterium-exchange-experiments and by the addition of O-, S-, and N-Nucleophiles to the exocyclic double bond of the model-dihydropyrromethenone (Z)-1 under very mild reaction conditions. Applying these results to the chemistry of 2,3-dihydro-bilatrienes-abc, their chemical characteristics—especially their tautomeric behavior and their dominant C-5-selectivity towards electrophiles—become better understandable.

     

Borax: An Ecofriendly and Efficient Catalyst for One-Pot Synthesis of 3,4-Dihydropyrimidine-2(1H)-ones under Solvent-Free Conditions

Borax in the presence of a very small amount of 5 M sulfuric acid efficiently catalyses the three-component condensation of an aldehyde, β-ketoester, and urea or thiourea to afford the corresponding 3,4-dihydropyrimidin-2(1H)-ones or 3,4-dihydropyrimidin-2(1H)-thiones in good to excellent yields under solvent-free conditions at 80 °C. Compared with the classical Biginelli reaction conditions, this new method has the advantage of excellent yield, short reaction time (1–2 h), easy workup, and no use of volatile organic solvent.     

Environmentally Friendly Preparation of 3,4-Dihydropyrimidin-2(1H)-thiones Catalyzed by Al(H2PO4)3

An efficient, facile, simple, and green synthetic protocol for the Biginelli reaction has been developed for the preparation of 3,4-dihydropyrimidin-2(1H)-thione derivatives under thermal and microwave irradiation, solvent-free conditions, in the presence of aluminum hydrogen phosphate, Al(H₂PO₄)₃, as an environmentally friendly heterogeneous recyclable catalyst, in high to excellent yields and short reaction time. In addition, the catalyst could be easily recovered from the reaction mixture by simple filtration and reused several times without any loss of activity.     

氯化亚锡催化“一锅法”合成N1-取代的3,4-二氢嘧啶-2(1H)-酮

以芳香醛、乙酰乙酸乙酯(甲酯)、单取代脲为原料,氯化亚锡为催化剂,在无溶剂、80℃条件下,通过三组分"一锅法"合成了一系列N1-取代的3,4-二氢嘧啶-2(1H)-酮衍生物。考察了催化剂用量和反应温度对产品收率的影响。通过IR、~1H NMR、~(13)C NMR和元素分析对目标产物结构进行确证,提出了可能的催化作用机理。本文的合成方法具有催化剂活性高、廉价易得和反应时间短、条件温和、产率高、绿色环保等优点。     

Preparation of Resin-Bound Bismethylene Cyclic Malonic Acid Ester and Facile Solid-Phase Synthesis of 2-Alkylthio-4(1H)-quinolone and 2-Alkyl-4(1H)-quinolone

Abstract

The resin-bound bismethylthiomethylene cyclic malonic acid ester 3 was built up efficiently. Resin 3 can react with arylamines and subsequent thermal cyclizations give 2-alkylthio-4-(1H)-quinolones. Furthermore, conjugate addition of Grignard reagents to the resin 3 forms the resin 6 which was reacted with aryl amines and subsequent thermal-cyclization-cleavages afford the 2-alkyl-4-(1H)-quinolones.     

[1,4]‐S‐ to O‐Silyl Migration: Multicomponent Synthesis of α‐Thioketones through Chemoselective Transformation of Esters to Ketones with Organolithium Reagents

A [1,4]‐S‐ to O‐silyl migration has been exploited to chemoselectively transform esters into ketones by using organolithium reagents, allowing multicomponent synthesis of α‐thioketones. Mechanistic studies reveal that this migration proceeds in an intramolecular manner and is more favorable than the corresponding [1,5]‐S‐ to O‐ and [1,3]‐C‐ to O‐silyl migrations. The resulting α‐thioketones are valuable building blocks for the synthesis of cyclic or multifunctionalized organosulfur compounds.     

Novel alkylations of cyclic thioureas by α-halocarboxylic acids and their esters. 4. Alkylation of 1-methyltetrahydropyrimidine-2(1H)-thione

Alkylation of 1-methyltetrahydropyrimidine-2(1H)-thione (N-methylpropylenethiourea) with chloro-and bromoacetic acids and their esters have given the 8-methyl-3-oxo-2,3,6,7-tetrahydro-5H-[1,3]thiazolo[3,2-a]pyrimidin-8-ium chloride or bromide. The former is readily hydrolyzed in 95% ethanol to 3-[(3-methylamino)propyl]-1,3-thiazolidine-2,4-dione hydrochloride while the second is more stable towards hydrolysis such that the corresponding hydrobromide is not separated. A paradoxical trend in the extent of the hydrolysis decreasing with the content of the water in the alcoholic solution comes to a complete stop in water. A possible explanation of this phenomenon is given. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1242–1251, August, 2006.     

Facile Synthesis of 6-Aryl-3-cyanopyridine-2-(1H)-thiones from Aryl Ketones

An improved synthesis of 6-aryl-3-cyanopyridine-2-(1H)-thiones utilizing enaminones as starting materials catalyzed by 1,4-diazabicyclo[2.2.2]octane (DABCO) was described. Moreover, a convenient one-pot conversion of aryl ketones to 6-aryl-3-cyanopyridine-2-(1H)-thiones was also developed in moderate to good yields (up to 80%).     

Formation of Contiguous Quaternary and Tertiary Stereocenters by Sequential Asymmetric Conjugate Addition of Grignard Reagents to 2‐Substituted Enones and Mg–Enolate Trapping

Herein a comprehensive study is provided on the asymmetric conjugate addition (ACA) of Grignard reagents to α‐substituted cyclic enones. After the elucidation of the optimal experimental conditions, the scope of Grignard reagents and Michael acceptors was examined. Whereas secondary Grignards gave better enantioselectivities with 2‐cyclopentenones, both linear and branched Grignard reagents were tolerated for the ACA to 2‐methylcyclohexenone. The sequential ACA–enolate trapping, which leads to quaternary stereocenters, was then studied. Thus, many electrophiles have been tested, thereby giving rise to highly functionalized cyclic ketones with contiguous α‐quaternary and β‐tertiary centers. The present technique is believed to bring a new approach to versatile terpenoid‐like skeletons of bioactive natural products. Straightforward derivatizations of enantioenriched saturated cyclic ketones further support the potential of the present methodology in synthesis.     

Studies on New Additions to 5-Methoxy-2 (5H)-Furanone: 1, 4-Addition of Grignard Reagents, and 1,3-Dipolar Cycloaddition of Silyl Nitronates

Recently, much effort has been made in the development of generally applicable organic synthesis of 5-alkyloxy-2(5H)-furanones due to their essential structure entities in the synthesis of some biologically active natural products and their application as useful intermediates in organic synthesis1. Their reactions such as Michael addition, Diels-Alder reaction and photocatalyzed conjugate addition have been studied extensively2-4.However, Michael addition reaction of Grignard reagents to 5-m…     

New data on the alkylation of cyclic thioureas with á-halocarboxylic acids and their esters. 2. Alkylation of tetrahydropyrimidine-2(1h)-thione and 5,5-dimethyltetrahydropyrimidine-2(1h)-thione

In the absence of bases all the attempted variations for the alkylation of tetrahydropyrimidine-2(1H)-thione with á-halocarboxylic acids gave only the bicyclic product-2-R-6,7-dihydro-5H-[1,3]thiazolo[3,2-a]pyrimidin-3(2H)-one hydrohalide. However the hydrohalide of the “ open” S-ethoxycarbonyl derivative of propyleneisothiourea can be obtained by treatment of tetrahydropyrimidine-2(1H)-thione with ethyl chloro-or bromoacetate in anhydrous acetone at room temperature. Alkylation of 5,5-dimethyltetrahydro-2(1H)-pyrimidinethione with chloro-or bromoacetic acid in anhydrous acetone at room temperature gave the hydrohalide of the “open” S-carboxymethyl derivative of dimethylpropyleneisothiourea. All remaining variations for the alkylation of this substrate with á-halocarboxylic acids or their esters gave only the corresponding bicyclic compounds-the hydrohalide of 2-R-6,6-dimethyl-6,7-dihydro-5H-[1,3]thiazolo[3,2-a]pyrimidin-3(2H)-one-independently of the reaction conditions. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, 593–604, April, 2006.     

利用三溴化铟催化的Biginelli反应原位合成3,4-二氢嘧啶-2-酮

一些二氢嘧啶酮衍生物具有重要的药物活性 ,可用作钙拮抗剂、降压剂和α1- 1 - a-拮抗剂 [1] .目前 ,从海洋生物中分离得到的一些具有生物活性的生物碱也具有二氢嘧啶酮的核 [2 ] .因此 ,近年来 ,这类化合物的合成已引起人们的极大兴趣 .文献 [3 ]采用乙酰乙酸乙酯、苯甲醛和脲在强酸性条件下进行原位缩合 ,得到二氢嘧啶酮的衍生物 ,但是该反应的产率不高 .三溴化铟作为一个温和的路易斯酸 [4 ,5] ,可以高效地催化此类反应 .在这一催化体系中 ,不仅 β-酮酸酯可以发生缩合反应 ,而且相对困难的 β-二酮也可以发生此类反应 ,使一些在传统 Bi…     

Regioselectivity, scope, and limitations of the addition of organolithium and allylmagnesium reagents to 1H-pyridine-2-thiones; access to 3,4-, 3,6-, and 5,6-dihydropyridine-2-thiones

Organolithium and lithium allyldibutylmagnesate reagents add to readily available NH, NMe, NBn, and NPh substituted pyridine-2-thiones yielding 4- and/or 6-substituted 3,4- or 3,6-dihydropyridine-2-thiones, respectively. The regioselectivity of the addition is dependent on the solvent, temperature, substituent at the nitrogen, and the type or organometallic reactant used, and allows tailoring of both systems. A simple conversion of 6-substituted β,γ-unsaturated δ-thiolactams into their α,β-unsaturated isomers makes the above processes a highly versatile synthetic methodology to access 6-substituted 5,6-dihydropyridine-2-thiones—valuable Michael acceptors.