Reactions of polyfluoroaromatic organozinc compounds with acyl chlorides and DMF

Article abstract of DOI:10.1135/cccc20081623

N,N-Dimethylbis(polyfluoroaryl)methanamines and polyfluoroarenes were obtained from polyfluoroaromatic organozinc compounds in DMF in the presence of acyl chlorides.

Full text of DOI:10.1135/cccc20081623

Polyfluoroaromatic Organozinc Compounds
1623
REACTIONS OF POLYFLUOROAROMATIC ORGANOZINC
COMPOUNDS WITH ACYL CHLORIDES AND DMF
1
2
Andrei S. VINOGRADOV , Vyacheslav I. KRASNOV and
3,
Vyacheslav E. PLATONOV *
N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry,
Siberian Division of Russian Academy of Sciences, Lavrentiev Ave. 9, 630090 Novosibirsk,
1
2
3
Russian Federation; e-mail: vas@nioch.nsc.ru, krasnov@nioch.nsc.ru, platonov@nioch.nsc.ru
Received April 18, 2008
Accepted October 6, 2008
Publish ed on lin e Decem ber 5, 2008
Dedicated to Professor Oldřich Paleta on the occasion of his 70th birthday and in recognition of his
contribution to organic fluorine chemistry.
N,N-Dim eth ylbis(polyfluoroaryl)m eth an am in es an d polyfluoroaren es were obtain ed from
polyfluoroarom atic organ ozin c com poun ds in DMF in th e presen ce of acyl ch lorides.
Keyw ord s: Polyfluoroarom atic organ ozin c com poun ds; DMF; Acyl ch lorides; N,N-Dim eth yl-
bis(polyfluoroaryl)m eth an am in es.
Th e preparation of polyfluoroarom atic organ ozin c com poun ds from
ch loropolyfluoroaren es an d Zn as well as from perfluoroaren es an d
Zn /Sn Cl2 in DMF was recen tly reported1–4. Ch em ical properties of th ese
organ ozin c com poun ds were studied. As a result, h ydro- an d brom o-
polyfluoroaren es, perfluorobiaryls1–3 an d allylpolyfluoroaren es4 h ave been
obtain ed. An oth er im portan t aspect of th e ch em istry of polyfluoroarom atic
organ ozin c com poun ds is th e reaction s of th e com poun ds with acyl ch lo-
rides in DMF for th e purpose of obtain in g polyfluoroarom atic keton es.
Acetyl (1a), propion yl (1b), pivaloyl (1c) an d ben zoyl ch lorides (1d ) were
used to in vestigate th e reaction s with C6F5Zn X (X = Cl, C6F5) (2) in som e
detail; it turn ed out th at pen tafluoroben zen e (3) an d N,N-dim eth yl-1,1-bis-
(perfluoroph en yl)m eth an am in e (4) were form ed in stead of th e expected
polyfluoroarom atic keton es. Th e reaction s of oth er polyfluoroarom atic
organ ozin c com poun ds with acyl ch loride 1d were perform ed to syn th esize
N,N-dim eth ylbis(polyfluoroaryl)m eth an am in es.
Collect. Czech. Chem. Commun. 2008, Vol. 73, No. 12, pp. 1623–1630
© 2008 Institute of Organic Chemistry and Biochemistry
doi:10.1135/cccc20081623

1624
Vinogradov, Krasnov, Platonov:
RESULTS AND DISCUSSION
Heatin g com poun d 2 with acyl ch lorides 1a, 1b resulted in th e form ation
of com poun d 3 wh ereas with acyl ch loride 1c th e reaction m ixture con -
tain ed am in e 4 alon g with 3 (Sch em e 1; Table I, run s 1–3).
Form ation of am in e 4 was observed wh en acyl ch loride 1d was used
(Sch em e 1). Wh en an equim olar ratio of acyl ch loride 1d or 1c an d 2 was
used in th e reaction , a con siderable am oun t of 2 was n ot con sum ed
(Table I, run s 3, 4). Wh en in creasin g th e am oun t of acyl ch loride 1d
(Table I, run 5), th e reaction of com poun d 2 occurred com pletely, leadin g
to a m ixture of com poun ds 3 an d 4.
SCHEME 1
TABLE I
Reaction s of com poun d 2 with acyl ch lorides
Reactan ts m olar
ratio 2/(1a–1d )
Ratio of 2:3:4
Run No.
R
(by 19F NMR)
1
2
3
4
5
Me (1a)
Et (1b)
1:2
3
1:2.2
1:1.1
1:1.1
1:2.5
3
Me3C (1c)
Ph (1d )
Ph (1d )
~5.1:1:1.3
~2.9:1:3
~0:1:1.5
We also perform ed th e reaction s of oth er organ ozin c reagen ts with acyl
ch loride 1d in DMF to syn th esize an alogues of am in e 4. Th us, from
organ ozin c reagen ts (5a–5d ), obtain ed from eth yl pen tafluoroben zoate,
pen tafluoroben zon itrile, pen tafluoropyridin e an d decafluoroin dan e un der
th e action of Zn /Sn Cl2 in DMF 2,4, th e correspon din g N,N-dim eth ylbis-
(polyfluoroaryl)m eth an am in es (6a–6d) alon g with polyfluoroaren es (7a–7d)
were syn th esized (Sch em e 2).
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Polyfluoroaromatic Organozinc Compounds
1625
SCHEME 2
In th e reaction of com poun d 5a with acyl ch loride 1d , am in e 6a an d
com poun d 7a are form ed alon g with a sm all am oun t of eth yl 4-ben zoyl-
2,3,5,6-tetrafluoroben zoate (8) an d dieth yl 2,2′,3,3′,5,5′,6,6′-octafluoro-
biph en yl-4,4′-dicarboxylate (9) accordin g to GC-MS an d 19F NMR.
Form ation of com poun d 3 from reagen t 2 an d acyl ch lorides 1a–1d as
well as of polyfluoroaren es 7a–7d from reagen ts 5a–5d an d ben zoyl ch lo-
ride (1d ) in DMF could occur as a result of tran sam idation . For exam ple,
th is process can in clude in term ediate form ation of am m on ium salts
(10a–10d ) an d th eir con version to am ides an d un stable form yl ch loride,
decom posin g to CO an d HCl 5,6. Th e reaction of HCl with reagen ts 2, 5a–5d
gives com poun ds 3, 7a–7d (Sch em e 3). It was sh own 5,6 th at tran sam idation
occurred un der severe reaction con dition s. Probably, th e presen ce of Zn Cl2
an d th e oth er zin c com poun ds as Lewis acids in th e studied reaction s pro-
m oted tran sam idation un der m ilder con dition s.
SCHEME 3
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1626
Vinogradov, Krasnov, Platonov:
An oth er direction of th e reaction of acyl ch lorides 1c an d 1d with DMF
is th e in teraction of electroph ilic cen tres of 1c an d 1d with oxygen of
DMF with th e form ation of Vilsm eier reactan ts7,8 11c, 11d an d/or 12c, 12d
(Sch em e 3). Form ation of am in e 4 can be ration alized by th e participation
of th e presen t reactan ts, an d also in term ediate com poun d 13. Th e latter re-
action with 2 probably gives am in e 4 (Sch em e 3). In a sim ilar m an n er, for-
m ation of am in es 6a–6d in th e reaction s of reagen ts 5a–5d with acyl
ch loride 1d could be explain ed.
Th e presen ce of (Ph CO)2O in th e reaction products of 2 an d 5a with acyl
ch loride 1d is con sisten t with th e participation of salt 12d in th e discussed
process of th e form ation of am in es 4 an d 6a. Form ation of (Ph CO)2O is
assum ed to proceed by th e reaction of 1d with 12d or Zn X(OCOR) (R = Ph ;
X = Cl, C6F5; Cl, 4-EtOCOC6F4). Th e participation of DMF in th e form ation
of am in es 4 an d 6a–6d is con sisten t with th e data on th e syn th esis of a
sim ilar com poun d (Me2NCH(CF=CFCF3)2) from organ ocadm ium reagen ts
(CF3CF=CFCdX) an d acyl ch loride 1d in DMF 9.
Prelim in arily, organ ozin c reagen ts 5a–5d were treated with CaCl2 to
decrease th e form ation of in active Ph COF. As sh own by a separate experi-
m en t, a m ixture of reagen t 2 an d Ph COF in DMF at 70 oC (4 h ) does n ot
appreciably ch an ge. Ph COF can be prepared from acyl ch loride 1d un der
th e action of Zn F2 10; th is salt m ay arise in th e form ation of organ ozin c
reagen ts 5a–5d .
Th e form ation of com poun d 8 is assum ed to proceed by th e reaction of
5a with acyl ch loride 1d ; product 9 could be form ed as a result of air oxida-
tion of com poun d 5a to eth yl 2,3,5,6-tetrafluoroph en yl-4-carboxylate radi-
cal with subsequen t couplin g.
CONCLUSION
In th e in vestigation of th e reaction s of polyfluoroarom atic organ ozin c com -
poun ds with acyl ch lorides an d DMF, th e m eth od of syn th esis of as yet
un described N,N-dim eth ylbis(polyfluoroaryl)m eth an am in es h as been de-
veloped. In th ese reaction s, th e form ation of polyfluoroaren es also took
place. As regards th e m ech an ism of form ation of N,N-dim eth ylbis(poly-
fluoroaryl)m eth an am in es an d polyfluoroaren es, th e participation of
Vilsm eier reactan ts an d tran sam idation in th e reaction s of acyl ch lorides
with DMF h ave been suggested. Furth er in vestigation of th e processes of
th is type will sh ed m ore ligh t on th ese problem s an d will also lead to a
better un derstan din g of th e syn th etic aspects of sim ilar reaction s.
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Polyfluoroaromatic Organozinc Compounds
1627
EXPERIMENTAL
NMR spectra were recorded on a spectrom eter Bruker AC-200 (188.3 MHz for 19F an d
200 MHz for 1H) for th e reaction m ixtures con tain in g organ ozin c com poun ds in DMF or
CCl4 solution . C6F6 (–162.9 ppm from CCl3F) an d (Me3Si)2O (0.04 ppm from TMS) were
used as in tern al stan dards. Ch em ical sh ifts (δ) are given in ppm relative to CCl3F an d TMS.
Couplin g con stan ts (J) are given in Hz. IR spectra were recorded on a Bruker Vector 22 IR
spectroph otom eter. UV spectra were m easured on a Hewlett–Packard 8453 UV spectroph oto-
m eter. Molecular weigh ts an d m olecular form ulae were determ in ed m ass-spectrom etrically
on a Fin n igan MAT 8200 h igh -resolution in strum en t (n om in al ion izin g electron en ergy 70 eV).
GC-MS an alyses were perform ed with a Hewlett–Packard G1800A apparatus (30 m capillary
colum n , HP-5). GLC an alyses were carried out on a Hewlett–Packard HP 5980 in strum en t
(30 m capillary colum n , HP-5). Meltin g poin ts were determ in ed in a Kofler block.
Organ ozin c com poun ds 2, 5a–5d were obtain ed by th e m eth ods described in refs2,4
.
To solution s of organ ozin c com poun ds 5a–5d , equim olar quan tity of CaCl2 (h eated at
250–300 °C for 3 h ) was added, an d th e resultin g m ixtures were stirred at room tem perature
for 3 h . Th e solution s of th e organ ozin c com poun ds were th en decan ted; th ese solution s
con tain ed ArfZn Cl an d (Arf)2Zn alon g with ArfH (Arf = C6F5, a–d , Sch em e 2) (19F NMR).
Assign m en ts of sign als in th e 19F NMR spectrum of am in e 6b were m ade on th e basis of
calculation (additive sch em e) usin g th e ch em ical sh ifts of th e ortho an d meta fluorin e atom s
11
of am in e 4 an d C6F5CN
.
19F NMR spectrum of 5-allyln on afluoroin dan e4 was used in as-
sign in g fluorin e sign als of am in e 6d .
Reaction s of Com poun ds 2 with Acyl Ch lorides 1a–1d
To a solution of 2 (7.28 g, 10.2 m m ol, purity 91%, with 9% of 3) acyl ch loride 1a (1.57 g,
20.0 m m ol) was added, th e m ixture was h eated at 60–65 °C for 4 h an d th en allowed to cool
to room tem perature. Th e reaction m ixture con tain ed on ly 3 (19F NMR). A sim ilar result was
obtain ed in th e reaction of 2 (22.64 g, 31.7 m m ol) with acyl ch loride 1b (6.51 g, 70.4 m m ol).
To a solution of 2 (7.87 g, 9.3 m m ol, purity 96%, with 4% of 3) acyl ch loride 1c (1.21 g,
10.0 m m ol) was added, th e m ixture was h eated at 60–65 °C for 4 h an d th en allowed to cool
to room tem perature. Th e reaction m ixture con tain ed 64% of th e in itial com poun d 2,
14% of com poun d 3 an d 18% of am in e 4 (19F NMR).
To a solution of 2 (3.94 g, 4.6 m m ol, purity 96%, with 4% of 3) acyl ch loride 1d (0.7 g,
5.0 m m ol) was added, th e m ixture was h eated at 60–65 °C for 4 h an d th en allowed to cool
to room tem perature. Th e reaction m ixture con tain ed 40% of th e startin g com poun d 2,
14% of 3 an d 42% of am in e 4 (19F NMR).
Reaction s of Com poun ds 2 with Ben zoyl Fluoride
To a solution of 2 (2.36 g, 2.8 m m ol, purity 96%, with 4% of 3) ben zoyl fluoride (0.37 g,
3.0 m m ol) was added, th e m ixture was h eated at 70 °C for 4 h an d th en allowed to cool to
room tem perature. Accordin g to th e 19F NMR spectrum , on ly th e sign als of th e startin g com -
poun ds were observed.
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Vinogradov, Krasnov, Platonov:
N,N-Dim eth ylbis(polyfluoroaryl)m eth an am in es. Gen eral Procedure
To a solution of a polyfluoroarom atic organ ozin c com poun d (2, 5a–5d ), acyl ch loride 1d
(3.52 g, 25.0 m m ol) was added, th e m ixture was h eated at 60–65 °C for 4 h an d th en al-
lowed to cool to room tem perature. Accordin g to 19F NMR, th e reaction m ixture con tain ed
43–73% of am in es (4, 6a–6d ), 7–42% of polyfluoroaren es (3, 7a–7d ) an d un iden tified im pu-
rities; in th e reaction s of 5b–5d with acyl ch loride 1d , th e form ation of Ph COF was observed
(
19F NMR, δ ~ 18 10). To th e reaction m ixture, 50 m l of water were added, an d th e organ ic
products were extracted with CHCl3 (3 × 5 m l). Each com bin ed extract was wash ed with
50 m l of 10% aqueous Na2CO3 an d 50 m l of water, dried over K2CO3, an d CHCl3 was dis-
tilled off. In th e reaction s with com poun ds 2, th e CHCl3 distilled con tain ed com poun d 3
(
19F NMR). To each residue obtain ed in th e reaction s with reagen ts 5b–5d (in oth er cases
th e residues were distilled in vacuo, ~3 Torr) an d each distillation fraction , 10 m l of dieth yl
eth er were added an d HCl was th en passed th rough th e solution to obtain th e h ydroch lor-
ides. Th e solid was filtered off an d wash ed with 5–10 m l of dieth yl eth er. For th e prepara-
tion of am in es 4, 6a–6d , 50 m l of 10% aqueous Na2CO3 were added to th e solid, an d th e
m ixture was h eated at 90–100 °C (10 m in ), th en allowed to cool to room tem perature. After
coolin g, th e am in e was filtered off an d wash ed with 50 m l of water.
N,N-Dimethyl-1,1-bis(perfluorophenyl)methanamine (4). From th e reaction of organ ozin c
com poun d 2 (7.14 g, 10 m m ol, purity 91%, with 9% of 3), th e fraction (1.32 g) with b.p.
117–127 °C con tain in g (GLC) am in e 4 (90%) an d th e fraction (0.88 g) with b.p. 172–173 °C
con tain in g am in e 4 (8%), Ph COOH (4%), (Ph CO)2O (84%) were obtain ed. Th e 19F NMR
spectrum of th e residue (0.21 g) did n ot give F sign als. From th e fraction s, h ydroch loride of
am in e 4 (1.01 g) an d th en am in e 4 (0.86 g, 44%) were isolated. Am in e 4, m .p. 53–54 °C. IR
(CCl4): 2995, 2961, 2874, 2828, 2779, 1651, 1522, 1505, 1124, 1006, 804. UV (EtOH (log ε)):
204 (4.14), 210 (4.14), 263 (3.25). 1H NMR (200 MHz, CCl4): 2.27 s, 6 H (Me); 5.12 s, 1 H
3
(CH). 19F NMR (188 MHz, CCl4): –162.3 m , 4 F (F-3 an d F-5); –154.8 t, 2 F, JFF = 21 (F-4);
–140.5 m , 4 F (F-2 an d F-6). MS, m/z (%): 391 (47) [M+], 347 (62) [M+ – NMe2], 278 (25), 224
(100) [M+ – C6F5], 42 (17), 28 (12). HRMS: foun d 391.03999, C15H7F10N [M] requires
391.04187. For C15H7F10N (391.2) calculated: 46.05% C, 1.80% H, 48.56% F, 3.58% N;
foun d: 46.16% C, 1.66% H, 48.03% F, 3.59% N.
Diethyl 4,4′-[(dimethylamino)methylene]bis(2,3,5,6-tetrafluorobenzoate) (6a). From th e reac-
tion of 5a (9.01 g, 10 m m ol, purity 95%, with 5% of eth yl 2,3,5,6-tetrafluoroben zoate (7a)),
th e fraction (1.41 g) with b.p. 80–170 °C con tain in g (GC-MS) N,N-dim eth ylben zam ide,
(Ph CO)2O, com poun ds 7a, 8, 9 an d am in e 6a were obtain ed. GC-MS, m/z (%): com poun d 8:
326 [M]+, 281 [C6H5COC6F4CO]+, 221 [C6F4CO2Et]+, 148 [C6F4]+, 105 [C6H5CO]+, 77 [C6H5]+,
51; com poun d 9: 442 [M]+, 397 [EtO2CC6F4C6F4CO]+, 386, 369 [EtO2CC6F4C6F4]+, 342, 324
[C6F4C6F4CO]+, 296 [C6F4C6F4]+, 176 [C6F4CO]+, 148 [C6F4]+, 45. 19F NMR spectrum of th is
fraction con tain ed sign als (–141.2, –139.5), wh ich were assign ed to keton e 8 by com parison
with th e 19F NMR spectrum of th e pure keton e. Accordin g to 19F NMR spectrum , th is frac-
tion con tain ed am in e 6a (47%), com poun d 7a (22%), keton e 8 (27%) an d com poun d 9
(4%). Th e residue (0.45 g) con tain ed m ain ly 6a; th e h ydroch loride (0.36 g) an d am in e 6a
(0.3 g, 12%) were isolated. Sim ilarly, th e fraction gave am in e 6a (0.6 g, 24%). Am in e 6a,
m .p. 78–79 °C. IR (CCl4): 2987, 2874, 2828, 2779, 1745, 1652, 1490, 1308, 1221, 1017, 985.
UV (EtOH (log ε)): 204 (4.34), 230 (4.30), 279 (3.59). 1H NMR (200 MHz, CCl4): 1.38 t, 6 H,
3
3JHH = 7.1 (CH2CH3); 2.31 s, 6 H (Me); 4.38 q, 4 H, JHH = 7.1 (CH2CH3); 5.23 s, 1 H (CH).
19F NMR (188 MHz, CCl4): –140.4 m , 4 F; –139.9 m , 4 F. MS, m/z (%): 499 (25) [M]+, 455
Collect. Czech. Chem. Commun. 2008, Vol. 73, No. 12, pp. 1623–1630

Polyfluoroaromatic Organozinc Compounds
1629
(12) [M+ – NMe2], 278 (100) [M+ – EtO2CC6F4], 250 (18). HRMS: foun d 499.10228,
21H17F8NO4 [M] requires 499.10297. For C21H17F8NO4 (499.4) calculated: 50.51% C,
C
3.43% H, 30.44% F, 2.80% N; foun d: 50.20% C, 3.41% H, 30.41% F, 2.73% N.
4,4′-[(Dimethylamino)methylene]bis(2,3,5,6-tetrafluorobenzonitrile) (6b). From th e reaction of
5b (8.93 g, 10 m m ol, purity 91%, with 9% of 2,3,5,6-tetrafluoroben zon itrile (7b)), th e corre-
spon din g h ydroch loride (1.05 g) an d th en am in e 6b (0.93 g, 46%) were isolated. Am in e 6b,
m .p. 112–114 °C. IR (CCl4): 3003, 2963, 2882, 2832, 2783, 2245, 1647, 1496, 1304, 995.
UV (EtOH (log ε)): 204 (4.32), 223 (4.30), 241 (4.42), 294 (3.71). 1H NMR (200 MHz, CCl4):
2.32 s, 6 H (Me); 5.32 s, 1 H (CH). 19F NMR (188 MHz, CCl4): –137.9 m , 4 F (F-2 an d F-6);
–132.6 m , 4 F (F-3 an d F-5). MS, m/z (%): 405 (52) [M]+, 361 (23) [M+ – NMe2], 292 (12), 231
(100) [M+ – NCC6F4]+, 42 (19). HRMS: foun d 405.05121, C17H7F8N3 [M] requires 405.05168.
For C17H7F8N3 (405.3) calculated: 50.38% C, 1.74% H, 37.51% F, 10.37% N; foun d:
50.37% C, 1.70% H, 37.19% F, 10.34% N.
N,N-Dimethyl-1,1-bis(perfluoropyridin-4-yl)methanamine (6c). From th e reaction of 5c (8.85 g,
10 m m ol, purity 93%, with 7% of 2,3,5,6-tetrafluoropyridin e (7c)), th e correspon din g h ydro-
ch loride (1.04 g) an d th en am in e 6c (0.83 g, 46%) were isolated. Am in e 6c, m .p. 86–87 °C.
IR (CCl4): 2994, 2964, 2907, 2877, 2833, 2784, 1643, 1477, 1262, 998. UV (EtOH (log ε)):
202 (4.07), 273 (3.82). 1H NMR (200 MHz, CCl4): 2.35 s, 6 H (Me); 5.35 s, 1 H (CH).
19F NMR (188 MHz, CCl4): –142.1 m , 4 F (F-2 an d F-6); 90.0 widen ed m , 4 F (F-3 an d F-5).
MS, m/z (%): 357 (25) [M]+, 313 (7) [M+ – NMe2], 207 (100) [M+ – NC5F4], 42 (22), 28 (23).
HRMS: foun d 357.05194, C13H7F8N3 [M] requires 357.05121. For C13H7F8N3 (357.2) calcu-
lated: 43.71% C, 1.98% H, 42.55% F, 11.76% N; foun d: 43.82% C, 1.96% H, 42.91% F,
11.66% N.
N,N-Dimethyl-1,1-bis(perfluoro-2,3-dihydro-1H-inden-5-yl)methanamine (6d ). From th e reac-
tion of 5d (12.50 g, 10 m m ol, purity 90%, with 10% of n on afluoroin dan e (7d )), th e corre-
spon din g h ydroch loride (1.42 g) an d th en am in e 6d (1.23 g, 40%) were isolated. Am in e 6d ,
m .p. 117–118.5 °C. IR (CCl4): 2994, 2964, 2877, 2832, 2783, 1650, 1503, 1327, 1254, 1205,
1162, 950. UV (EtOH (log ε)): 205 (4.47), 277 (3.59). 1H NMR (200 MHz, CCl4): 2.34 s, 6 H
(Me); 5.35 s, 1 H (CH). 19F NMR (188 MHz, CCl4): –140.6 m , 2 F (F-7); –131.2 quin , 4 F,
3JFF = 4.5 (F-2); –122.0 m , 2 F (F-6); –115.5 m , 2 F (F-4); –109.0 an d –108.2 both m , 8 F (F-1
an d F-3). MS, m/z (%): 616 (2) [M]+, 572 (13) [M+ – NMe2], 336 (100) [M+ – C9F9], 42 (10).
HRMS: foun d 615.02898, C21H7F18N [M] requires 615.02909. For C21H7F18N (615.3) calcula-
ted: 40.99% C, 1.15% H, 55.58% F, 2.28% N; foun d: 41.25% C, 1.31% H, 55.34% F, 2.06% N.
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