Methodologies for the synthesis of quaternary carbon centers via hydroalkylation of unactivated olefins: twenty years of advances

• Thiago S. Silva and
• Fernando Coelho

Beilstein J. Org. Chem. 2021, 17, 1565–1590, doi:10.3762/bjoc.17.112

• also tolerable to functional groups, such as silyl ethers (52a), carbamates (52b), and heterocycles (52c), present in the olefin moiety. The initial mechanism proposed by the authors begins with the formation of Fe(III) hydride species (A), followed by hydrogen atom transfer to the olefin in a

Stereoselective synthesis and transformation of pinane-based 2-amino-1,3-diols

• Ákos Bajtel,
• Mounir Raji,
• Matti Haukka,
• Ferenc Fülöp and
• Zsolt Szakonyi

Beilstein J. Org. Chem. 2021, 17, 983–990, doi:10.3762/bjoc.17.80

• aminohydroxylation process starting from allylic carbamates usually carried out in the presence of potassium osmate [24][25][26][27][28]. In recent years, we have extensively studied the stereoselective synthesis, as well as catalytic and pharmacological applications of monoterpene-based 3-amino-1,2-diols, which are

Prins cyclization-mediated stereoselective synthesis of tetrahydropyrans and dihydropyrans: an inspection of twenty years

• Asha Budakoti,
• Pradip Kumar Mondal,
• Prachi Verma and
• Jagadish Khamrai

Beilstein J. Org. Chem. 2021, 17, 932–963, doi:10.3762/bjoc.17.77

• -one. Mechanism for the Lewis acid-catalyzed synthesis of tetrahydropyran-4-one. Hoveyda and co-workers’ strategy for 2,6-disubstituted 4-methylenetetrahydropyran. Funk and Cossey’s ene-carbamates strategy. Yadav and Kumar’s cyclopropane strategy for THP synthesis. 2-Arylcylopropylmethanolin in

Synthetic reactions driven by electron-donor–acceptor (EDA) complexes

• Zhonglie Yang,
• Yutong Liu,
• Kun Cao,
• Xiaobin Zhang,
• Hezhong Jiang and
• Jiahong Li

Beilstein J. Org. Chem. 2021, 17, 771–799, doi:10.3762/bjoc.17.67

• trifluoromethylation (Scheme 25). A variety of olefins, such as ene carbamates, styrene, aliphatic olefins, vinyl ethers, and acrylates are compatible in this approach, affording corresponding β-(trifluoromethyl)alkynes with good to excellent yield. The bifunctionalization was achieved by an EDA-complex-initiated

Coupling biocatalysis with high-energy flow reactions for the synthesis of carbamates and β-amino acid derivatives

• Alexander Leslie,
• Thomas S. Moody,
• Megan Smyth,
• Scott Wharry and
• Marcus Baumann

Beilstein J. Org. Chem. 2021, 17, 379–384, doi:10.3762/bjoc.17.33

• . A variety of different acid substrates including benzoic acids, phenylacetic acids, and various non-aromatic acids successfully underwent the above continuous Curtius rearrangement process giving the desired Cbz-carbamates in good yields (Figure 1). As expected, benzoic acids cleanly and rapidly

• rearranged within a residence time of 30 minutes rendering the corresponding carbamates 3a–e in high chemical yields. Phenylacetic acid species were found to be less reactive substrates that rearranged more slowly (tRes = 60 min) and thus giving lower yields (3f–h). Moreover, the formation of urea side

• migratory aptitude which in turn translated into a higher chemical yield towards the corresponding carbamate structure 3i. Lastly, a set of non-aromatic acids was subjected to the same reaction conditions providing access to carbamates bearing cyclohexyl, cyclobutyl, and vinylic appendages (3j–m). An

Chan–Evans–Lam N1-(het)arylation and N1-alkеnylation of 4-fluoroalkylpyrimidin-2(1H)-ones

• Viktor M. Tkachuk,
• Oleh O. Lukianov,
• Mykhailo V. Vovk,
• Isabelle Gillaizeau and
• Volodymyr A. Sukach

Beilstein J. Org. Chem. 2020, 16, 2304–2313, doi:10.3762/bjoc.16.191

• cyclocondensation of N-(trifluorochloroethylidene) carbamates IV with β-amino crotonates V led only to 4-trifluoromethylpyrimidin-2(1H)-ones I bearing a 5-alkoxycarbonyl substituent (R3/6 = CO2Alk) due to the strong structural limitations of the nucleophilic enamine component (see Figure 1а, method В) [31]. The

Photosensitized direct C–H fluorination and trifluoromethylation in organic synthesis

• Shahboz Yakubov and
• Joshua P. Barham

Beilstein J. Org. Chem. 2020, 16, 2151–2192, doi:10.3762/bjoc.16.183

•  26B). The reaction conditions were also amenable to carbamates, affording the products 64–67 in moderate to good yield (42–58%). That the carbamate oxygen atom could direct the fluorination α to itself instead of α to the amide nitrogen atom provided an inverted, complementary selectivity as expected

• previously for benzylic fluorination [130]. In a later perspective [36], the authors speculated that the amide served as a directing group. Indeed, in situ-formed ammonium carbamates were recently identified to direct the HAT of a quinuclidinium radical cation [208]. 3.5 Scalability of C–H fluorinations That

Azidophosphonium salt-directed chemoselective synthesis of (E)/(Z)-cinnamyl-1H-triazoles and regiospecific access to bromomethylcoumarins from Morita–Baylis–Hillman adducts

• Soundararajan Karthikeyan,
• Radha Krishnan Shobana,
• Kamarajapurathu Raju Subimol,
• J. Helen Ratna Monica and
• Ayyanoth Karthik Krishna Kumar

Beilstein J. Org. Chem. 2020, 16, 1579–1587, doi:10.3762/bjoc.16.130

• chemists. Accordingly, MBH adducts have been explored as strategic intermediates for the synthesis of interesting molecules, such as carbamates of unsaturated β-amino acids [1], β-phenylsylfenyl-α-cyanohydrocinnamaldhydes [2], 2-alkylcarbonyl-1-indanols [3], dihydropyrazoles [4], tetrahydroacridines [5], γ

Recent synthesis of thietanes

• Jiaxi Xu

Beilstein J. Org. Chem. 2020, 16, 1357–1410, doi:10.3762/bjoc.16.116

• in low to good yields by the reaction of 2-(1-haloalkyl)oxiranes 142 and 147 with ammonium monothiocarbamates 148 as the sulfur nucleophiles. First, a nucleophilic ring-opening of the oxiranes 142 and 147 by monothiocarbamates 148 gave rise to the S-(γ-halo-β-hydroxyalkyl)carbamates 149 with release

• of amines. The latter then aminolyzed the carbamates 149 to generate ureas 151 and γ-halo-β-hydroxyalkanethiols 150. The intermediates 150 further underwent an intramolecular cyclization to produce the thietane-3-ols 145 in low to good yields [58] (Scheme 30). Paclitaxel (Taxol®) and docetaxel

Photocatalysis with organic dyes: facile access to reactive intermediates for synthesis

• Stephanie G. E. Amos,
• Marion Garreau,
• Luca Buzzetti and
• Jerome Waser

Beilstein J. Org. Chem. 2020, 16, 1163–1187, doi:10.3762/bjoc.16.103

• -systems: heteroarenes and electron-poor alkenes in particular. Using the tools of organophotocatalysis, this reactive intermediate can be directly obtained from carbonyl derivatives, such as aldehydes, α-keto acids, oxalates, or carbamates through oxidative or reductive decarboxylations, oxidative

Accelerating fragment-based library generation by coupling high-performance photoreactors with benchtop analysis

• Quentin Lefebvre,
• Christophe Salomé and
• Thomas C. Fessard

Beilstein J. Org. Chem. 2020, 16, 982–988, doi:10.3762/bjoc.16.87

• of complex amines: bicyclopentanamines, azetidines, spiroazetidines, spiropyrrolidines and spiropiperidines. Functional group tolerance was probed by using functionalized building blocks bearing esters, carbamates, alcohols, tertiary amines, ethers, sulfones and fluorine atoms (Scheme 2 and Scheme 3

Photocatalytic deaminative benzylation and alkylation of tetrahydroisoquinolines with N-alkylpyrydinium salts

• David Schönbauer,
• Carlo Sambiagio,
• Timothy Noël and
• Michael Schnürch

Beilstein J. Org. Chem. 2020, 16, 809–817, doi:10.3762/bjoc.16.74

• group were investigated. Instead of the N-phenyl group, other protecting groups such as acetyl, benzoyl, or carbamates were tested, but the corresponding starting materials proved to be unreactive in the desired transformation. The use of substituted N-phenyl groups revealed that almost all of the

p-Pyridinyl oxime carbamates: synthesis, DNA binding, DNA photocleaving activity and theoretical photodegradation studies

• Panagiotis S. Gritzapis,
• Panayiotis C. Varras,
• Nikolaos-Panagiotis Andreou,
• Katerina R. Katsani,
• Konstantinos Dafnopoulos,
• George Psomas,
• Zisis V. Peitsinis,
• Alexandros E. Koumbis and
• Konstantina C. Fylaktakidou

Beilstein J. Org. Chem. 2020, 16, 337–350, doi:10.3762/bjoc.16.33

• DNA-photocleavers, and are proposed as new leads for “on demand” biotechnological applications in drug discovery and medicine. Keywords: DNA binding; DNA photocleavage; N–O homolysis; oxime carbamates; photocleavage agents; Introduction Small organic molecules able to bind DNA provide promises for

• radicals are also produced from 2-(1-naphthylmethyl)imidazoline [35], whereas acylaminyl radicals [R(COR)N∙] are formed from the photocleavage of the N–O bond of N,O-diacyl-N-phenylhydroxylamines, along with a carbonyloxyl radical [38]. The photochemistry of O-carbamoyl oximes (or oxime carbamates) is well

• studied. These compounds are categorized as highly photoreactive photobase generators (PBGs), providing amines upon rapid decarboxylation of the initially formed carbamoyloxyl radicals (R2NCOO∙) [49][50][51][52][53]. To the best of our knowledge oxime carbamates have never been photocleaved in the

Rapid, two-pot procedure for the synthesis of dihydropyridinones; total synthesis of aza-goniothalamin

• Thomas J. Cogswell,
• Craig S. Donald and
• Rodolfo Marquez

Beilstein J. Org. Chem. 2020, 16, 135–139, doi:10.3762/bjoc.16.15

• , acrylamide was used in an analogous manner to the carbamates employed by Veenstra (Scheme 1) [19]. In our initial attempts, the solvent was changed from dichloromethane to acetonitrile due to solubility issues with the acrylamide and the postulated imine intermediate. The reaction proved sluggish, taking

Recent advances in transition-metal-catalyzed incorporation of fluorine-containing groups

• Xiaowei Li,
• Xiaolin Shi,
• Xiangqian Li and
• Dayong Shi

Beilstein J. Org. Chem. 2019, 15, 2213–2270, doi:10.3762/bjoc.15.218

New α- and β-cyclodextrin derivatives with cinchona alkaloids used in asymmetric organocatalytic reactions

• Iveta Chena Tichá,
• Simona Hybelbauerová and
• Jindřich Jindřich

Beilstein J. Org. Chem. 2019, 15, 830–839, doi:10.3762/bjoc.15.80

• demanding cinchona groups. Additionally, some of these new CD derivatives showed promising results of up to 75% ee in the AAA reactions of Morita–Baylis–Hillman (MBH) carbamates and significant differences depending on the attached cinchona alkaloid (cinchonine, cinchonidine, quinine, quinidine) as well as

Tandem copper and photoredox catalysis in photocatalytic alkene difunctionalization reactions

• Nicholas L. Reed,
• Madeline I. Herman,
• Vladimir P. Miltchev and
• Tehshik P. Yoon

Beilstein J. Org. Chem. 2019, 15, 351–356, doi:10.3762/bjoc.15.30

• we have proposed for photocatalytic oxyamination is outlined in Figure 1c. Photoinduced one-electron oxidation of an appropriately electron-rich styrene 1 results in the formation of a radical cation 1•+ that is susceptible to attack by various heteroatomic nucleophiles, including carbamates [21][22

Sigmatropic rearrangements of cyclopropenylcarbinol derivatives. Access to diversely substituted alkylidenecyclopropanes

• Guillaume Ernouf,
• Jean-Louis Brayer,
• Christophe Meyer and
• Janine Cossy

Beilstein J. Org. Chem. 2019, 15, 333–350, doi:10.3762/bjoc.15.29

• generate the reactive species by dehydration of carbamates under mild conditions and the ultimate formation of isocyanates which can be derivatized in situ [54]. The conditions were optimized with alcohol 25 substituted by a 2-phenylethyl group at the oxygen-bearing carbon atom (C4) and possessing gem

• , reaction with pyrrolidine, imidazole, methanol, allyl alcohol, benzyl alcohol and 9-fluorenemethanol (FmOH) provided the corresponding urea 30, N-carbamoyl imidazole 31 and carbamates 32–35, respectively, in good yields (69–80%). The reaction of isocyanate 28 with tert-butanol was sluggish even by heating

• with allyl alcohol. Benzylidenecyclopropane 41 was also obtained in good yield (70%) but the efficiency of the sigmatropic rearrangement dropped for carbamates in which the aromatic group at C4 is substituted by an electron-withdrawing group at the para-position. Indeed, N-Alloc (arylmethylene

Stereodivergent approach in the protected glycal synthesis of L-vancosamine, L-saccharosamine, L-daunosamine and L-ristosamine involving a ring-closing metathesis step

• Pierre-Antoine Nocquet,
• Aurélie Macé,
• Frédéric Legros,
• Jacques Lebreton,
• Gilles Dujardin,
• Sylvain Collet,
• Arnaud Martel,
• Bertrand Carboni and
• François Carreaux

Beilstein J. Org. Chem. 2018, 14, 2949–2955, doi:10.3762/bjoc.14.274

• synthesis of the carbamate-protected glycal of L-vancosamine 1 and L-saccharosamine 2 were prepared in two steps by treatment of alcohols with the trichloroacetyl isocyanate reagent (TCA-NCO) followed by basic hydrolysis. The spectroscopic properties of carbamates 17 were identical to those reported in the

• afford the epimeric product 26. Both diastereomers 23 and 26 were converted to the corresponding known carbamates using a two step sequence. Reaction with TCA-NCO followed by a basic hydrolysis provided the desired compounds 24 and 27 in good yields and in full agreement with all reported spectroscopic

Applications of organocatalysed visible-light photoredox reactions for medicinal chemistry

• Michael K. Bogdos,
• Emmanuel Pinard and
• John A. Murphy

Beilstein J. Org. Chem. 2018, 14, 2035–2064, doi:10.3762/bjoc.14.179

• carbamates, urea and non-basic heterocycles (Scheme 11) [54]. The scope covers a multitude of electron-poor and electron-rich arenes which can be reacted with carbamates, urea, pyrazole and triazole derivatives to furnish aminated products. The authors address the various reactivities observed with respect

An amine protecting group deprotectable under nearly neutral oxidative conditions

• Shahien Shahsavari,
• Chase McNamara,
• Mark Sylvester,
• Emily Bromley,
• Savannah Joslin,
• Bao-Yuan Lu and
• Shiyue Fang

Beilstein J. Org. Chem. 2018, 14, 1750–1757, doi:10.3762/bjoc.14.149

• including 3a–d gave good to excellent isolated yields of carbamates 5a–d (Table 1, entries 1–4). Under these conditions, however, secondary aliphatic amines could not react or could react but gave very low yields. We tried a variety of other conditions such as deprotonating the amine followed by reacting

• any special devices such as an electrochemical cell. Therefore, the dM-Dmoc carbamates were first oxidized with sodium periodate at room temperature. After removing the excess oxidizing agent and other inorganic salts by filtration, β-elimination to give the amine products was initiated with the weak

• . General procedure for dM-Dmoc protection of aliphatic amines – synthesis of carbamates 5a–d: To a solution of an amine (0.292 mmol, 1 equiv) and DIPEA (0.255 mL, 1.46 mmol, 5 equiv) in dry THF (10 mL) was added 4 (0.100 g, 0.292 mmol, 1 equiv) at rt under argon. After stirring for 8 h, the reaction was

Hypervalent organoiodine compounds: from reagents to valuable building blocks in synthesis

• Gwendal Grelier,
• Benjamin Darses and
• Philippe Dauban

Beilstein J. Org. Chem. 2018, 14, 1508–1528, doi:10.3762/bjoc.14.128

• carbamates [92], sulfamates [94][95][96][97], ureas and guanidines [98], sulfamides [99], hydroxylamine-derived sulfamates [100], carbamimidates [101], and sulfonimidamides [102][103][104][105][106][107]. These reactions involve the formation of a metal-bound nitrene that can insert into a C(sp3)–H bond or a

London dispersion as important factor for the stabilization of (Z)-azobenzenes in the presence of hydrogen bonding

• Andreas H. Heindl,
• Raffael C. Wende and
• Hermann A. Wegner

Beilstein J. Org. Chem. 2018, 14, 1238–1243, doi:10.3762/bjoc.14.106

• than LD interactions and are mainly responsible for the observed stabilization effects, which is also represented as a blue surface in the NCI plot of (R,S)-4 c1. Furthermore, it is known that amides form stronger hydrogen bonds than carbamates and the strength also depends on the steric bulk of the

Anodic oxidation of bisamides from diaminoalkanes by constant current electrolysis

• Tatiana Golub and
• James Y. Becker

Beilstein J. Org. Chem. 2018, 14, 861–868, doi:10.3762/bjoc.14.72

• ). It has been found that anodic methoxylation of amides (and carbamates) can be utilized to form new carbon–carbon bonds [6][7] (Scheme 2). Furthermore, this anodic route could also be important from a synthetic point of view, affording ring-expansion [8][9][10] and annulation of rings [1][11][12

Cobalt-catalyzed directed C–H alkenylation of pivalophenone N–H imine with alkenyl phosphates

• Wengang Xu and
• Naohiko Yoshikai

Beilstein J. Org. Chem. 2018, 14, 709–715, doi:10.3762/bjoc.14.60

• mild and efficient C–H alkenylation of N-pyrimidylindoles and pyrroles with alkenyl acetates using a cobalt–NHC catalyst (Scheme 1a) [17]. The same catalytic system also promoted the alkenylation using alkenyl carbamates, carbonates, and phosphates. More recently, we have achieved an N-arylimine