2-Isothiocyanatobenzylpyridinium bromide - An intermediate for the synthesis of 2-arylamino-4H-benzo[d][1,3]thiazines

Gonda, Jozef; Kristián, Pavol

doi:10.1135/cccc19862810

Cited by 11 publications

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“…Since the signal of the NH group in the 1 H NMR spectrum of the solution of the compound obtained from thiourea 3b appears at 7.25-7.33 ppm (see Table 2 and our previous work [24]), which is in accord with the chemical shifts of the corresponding protons of the compounds 4a-i, and 5a,c,d (Table 2) and with the chemical shifts of the corresponding protons described in the literature for this type of heterocyclic compounds [20][21][22][23], it is quite likely that the heterocyclic product, which is formed upon the rearrangement of 3b, is present in solution as 2-amino-4H-3,1-benzothiazine 5b, though that this product exists in the crystal as tautomer 6b.…”

supporting

confidence: 80%

“…* 2 The designations R for 4a-i are the same as for 2a-i. An additional finding confirming the correct identification of the transformation products of cyclopropanes 2a-i and 3a-d was the total correlation of the spectral characteristics of heterocycles 4a-i and 5a-c ( Table 2) with the corresponding characteristics of numerous analogs (see, for example, the work of various authors [20][21][22][23]). _______ * The 1 H NMR spectra were taken in CDCl 3 for 2a-e,g,h, and 3a-c and in DMSO-d 6 for 2f, i, 4a-i, and 5a-d. * 2 Here and subsequently, the atoms in the aryl substituent R are indicated with a prime sign.…”

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confidence: 72%

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Synthesis of 2-amino-4H-3,1-benzoxazines and 2-amino-4H-3,1-benzothiazines by the rearrangement of o-cyclopropylphenylureas and o-cyclopropylphenylthioureas

Федотов

Трофимова

Romanov

et al. 2008

Chem Heterocycl Comp

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Syntheses are reported for 2-cyclopropylphenylureas and 2-cyclopropylphenylthioureas and the behavior of these compounds was studied under conditions for the acid-catalyzed opening of the cyclopropyl ring. Upon the action of concentrated sulfuric acid or trifluoroacetic acid, these ureas and thioureas can undergo rearrangement to the corresponding 3,1-benzoxazines and 3,1-benzothiazines.Functionally-substituted cyclopropanes, which have now become readily available, are finding increasing use as starting compounds in the synthesis of various organic compounds produced by the transformation of the three-membered ring upon the action of specific reagents. These transformations may yield either saturated or unsaturated acyclic products of opening of the cyclopropyl ring [1-4] or carbo-and heterocycles [5][6][7][8][9][10][11]. An especially large number of studies have been devoted to donor-acceptor functionally-substituted cyclopropanes [11]. The reactions in this case proceed predominantly with the participation or effect of the substituents directly bound to the three-carbon ring. There has been considerably less work on the transformations of cyclopropane compounds, in which the substituents, not directly bound to the cyclopropane ring, participate in the reaction. Nevertheless, examples of such transformations [9,[12][13][14] show that the synthetic scope of functionally-substituted cyclopropanes may be considerably expanded. Here, definite promise is found in intramolecular acid-catalyzed ortho-substituted arylcyclopropanes due to the unique ortho-orienting effect of the cyclopropane substituent in electrophilic nitration reactions [15][16][17]. These reagents are now readily available.In a search for new examples of the intramolecular rearrangement of ortho-functionally-substituted arylcyclopropanes, we synthesized 2-cyclopropylphenylureas and 2-cyclopropylphenylthioureas and studied their transformations in trifluoroacetic and concentrated sulfuric acids. We assumed that the acid-catalyzed opening of the cyclopropane ring in suitable cyclopropylureas and cyclopropylthioureas would initiate reaction of the resultant benzylic carbenium ion with the internal nucleophile (urea or thiourea fragment) to form 2-amino-3,1-benzoxazines and 3,1-benzothiazines or isomeric compounds. _______ * Deceased. __________________________________________________________________________________________

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confidence: 80%

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confidence: 72%

Synthesis of 2-amino-4H-3,1-benzoxazines and 2-amino-4H-3,1-benzothiazines by the rearrangement of o-cyclopropylphenylureas and o-cyclopropylphenylthioureas

Федотов

Трофимова

Romanov

et al. 2008

Chem Heterocycl Comp

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“…In our previous papers [1][2][3][4] we studied the synthesis and reactions of 2-bromomethylphenyl isothiocyanate (1) in regard to the selective reaction of its reaction centers (the bromine atom and the NCS group) with nucleophilic reagents, The synthetic utilization of isothiocyanates with reactive halogen atom in the preparation of heterocyclic compounds is well known s -s . Less attention, however, has been paid to analogous reactions of the corresponding halogeno isocyanates 9 ,10. The present work is aimed at the synthesis of 2-alkyl-(aryl)amino-4H-3,1-benzoxazines IV from 2-bromomethylphenyl isocyanate (11) (which is more reactive than the 2-chloromethyl derivative) and a set of primary aliphatic or aromatic amines.…”

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confidence: 99%

Simple and efficient synthesis of 4H-3,1-benzoxazines from 2-bromomethylphenyl isocyanate and amines

Gonda

Barnikol

1990

Collect. Czech. Chem. Commun.

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Reaction of 2-bromomethylphenyl isocyanate (II; prepared by radical bromination of 2-tolyl isocyanate with N-bromosuccinimide) with aliphatic and aromatic amines takes place on the NCO group under formation of stable N-alkyl(aryl)-N'-(2-bromomethylphenyl)ureas III. On treatment with sodium hydrogen carbonate in water or sodium hydride in N,N-dimethylformamide, the ureas III are cyclized to give 2-alkyl(aryl)amino-4H-3,1-benzoxazines IV in good yields. Reaction of isocyanate II with alcohols leads to alkyl 2-bromomethylphenyl carbamates. Structure of the synthesized compounds has been proven by spectral methods and elemental analysis.In our previous papers 1-4 we studied the synthesis and reactions of 2-bromomethylphenyl isothiocyanate (1) in regard to the selective reaction of its reaction centers (the bromine atom and the NCS group) with nucleophilic reagents, The synthetic utilization of isothiocyanates with reactive halogen atom in the preparation of heterocyclic compounds is well known s -s . Less attention, however, has been paid to analogous reactions of the corresponding halogeno isocyanates 9 ,10.The present work is aimed at the synthesis of 2-alkyl-(aryl)amino-4H-3,1-benzoxazines IV from 2-bromomethylphenyl isocyanate (11) (which is more reactive than the 2-chloromethyl derivative) and a set of primary aliphatic or aromatic amines. 4H-3,1-Benzoxazines are tranquilizers and exhibit strong anxiolytic effects: two known compounds of this type, ethyfoxin II and brofoxin 12, may be mentioned.Traditional approaches to 4H-3,1-benzoxazines use cycIization of N-acylaminobenzyl alcohols!3 and N-aryl-N' -(2-hydroxymethylphenyl)ureas I4 with concentrated hydrobromic acid. These compounds can also be prepared by reaction of 2-aminobenzyl halides with glacial acetic acid l4 . Other routes leading to 4H-3,1--benzoxazines make use of condensation reactions of 2-aminobenzyl alcohols with aldehydes lS or cyclization of N,N-dialkyl-N'-(2-chloromethylphenyl)ureas, prepared from 2-chloromethyl isocyanates and dialkylanilines 16 .2-Bromomethylphenyl isocyanate (ll) was prepared in 78% yield by radical bromination of 2-tolyl isocyanate with N-bromosuccinimide in the presence of di-

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“…The product was obtained as a pinkish solid; R f = 0.50 (SiO 2 , hexane/EtOAc = 8:2); purification system: CombiFlash MPLC (hexane/EtOAc = 85:15); yield: 254 mg (94%); mp 180–181 °C (lit . 179–180 °C); 1 H NMR (400 MHz, DMSO- d 6 ): δ 9.27 (br, 1H), 7.74 (s, 2H), 7.24–7.14 (m, 2H), 7.00 (d, J = 7.6 Hz, 2H), 6.86 (d, J = 7.6 Hz, 2H), 3.98 (s, 2H), 3.71 (s, 3H) ppm; 13 C{ 1 H} NMR (100 MHz, DMSO- d 6 ): δ 155.2, 150.7, 145.0, 135.4, 128.3, 127.2, 123.3, 121.9, 120.8, 114.8, 114.2, 113.5, 55.6, 29.1 ppm; MS (APCI): [M + 1] + , 271.1 (99.78%); HRMS (ESI-QTOF, [M + H] + ): calcd for C 15 H 15 N 2 OS, 271.0905; found, 271.0903.…”

Section: Methodsmentioning

confidence: 99%

Reagent-Controlled Divergent Synthesis of 2-Amino-1,3-Benzoxazines and 2-Amino-1,3-Benzothiazines

et al. 2019

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A reagent-controlled chemoselective process has been devised for the synthesis of 4H-1,3-benzoxazines and related biologically important heterocycles in high yields under mild conditions. These scaffolds could be efficiently constructed using two different chemoselective reactions that rely on the choice of reagents and reaction conditions. The treatment of various 2-amino-arylalkyl alcohols with isothiocyanates afforded thiourea intermediates, which were reacted in situ with molecular iodine in the presence of triethylamine to give 2-amino-4H-1,3-benzoxazines, whereas the corresponding 2-amino-4H-1,3-benzothiazines were obtained by the reaction of thiourea intermediates in the presence of T3P (a mild cyclodehydrating agent) and triethylamine as the base. The described protocol represents the first example for the synthesis of 4H-1,3-benzoxazines via the dehydrosulfurization method using molecular iodine as the reagent.

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2-Isothiocyanatobenzylpyridinium bromide - An intermediate for the synthesis of 2-arylamino-4H-benzo[d][1,3]thiazines

Cited by 11 publications

References 0 publications

Synthesis of 2-amino-4H-3,1-benzoxazines and 2-amino-4H-3,1-benzothiazines by the rearrangement of o-cyclopropylphenylureas and o-cyclopropylphenylthioureas

Synthesis of 2-amino-4H-3,1-benzoxazines and 2-amino-4H-3,1-benzothiazines by the rearrangement of o-cyclopropylphenylureas and o-cyclopropylphenylthioureas

Simple and efficient synthesis of 4H-3,1-benzoxazines from 2-bromomethylphenyl isocyanate and amines

Reagent-Controlled Divergent Synthesis of 2-Amino-1,3-Benzoxazines and 2-Amino-1,3-Benzothiazines

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