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BNC Isosteres of Cyclopropane and a Borylated Diazoester from Diazo Compounds and (Dimethylamino)bis(trifluoromethyl)borane.

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C0M M U N I C A T 1 0 N S
Table 1. Selected spectroscopic data of 2-5 [a].
2 . ' H NMR. 6 = 2.01 (S. 2 H ; CH,). 2.78 ( s , 6 H ; CH,): "C('H) NMR:
6 = 40.7 (broad). 47.18 (sept. 4J(C.F) = 2.1 Hz); "B N M R : 6 = -16.3 (sept.
'J(B,F) -30 Hz); '"F N M R . d = - 59.4 (q, 'J(F,Bj -30 Hz); IR(gasj:
C[cm-'] =1140, 1100 (C-F).
3: 'HNMR:6=0.20(s,9H;CH,),1.35(s,IH;CH),2.82(s,3H;CH,),2.84
(5. 3 H ; CH,): "C('H) N M R : b = - 0.15 (4. '4C.F) =1.7 Hz), -44.4
(broad). 45.46 (q "J(C.F) = 2.6 Hz), 50.14 (q, &J(C,F)= 2.4 Hz); "B N M R :
6 = - 15.3 (sept. 'J(B.F) -34 Hz);I9FN M R : 6 = - 57.3 ("d", -60.5 ("d");
1R (KBrj: ?[cm-'] =1108. 1085 (C-F).
4: 'HNMR:6=0.08(s.9H;CH,).2.83(s.3H,CH,).3.00(s.3H;CH,),3.30
BNC Isosteres of Cyclopropane and a Borylated
Diazoester from Diazo Compounds and
(Dimethylamino)bis(trifluoromethyl)borane**
By Andreas Ansorge, David J. Brauer, Hans Burger,*
Thomas Hagen, and Gottfried Pawelke
la] ' H N M R : 250 MHz, CDCI,, 25 C, 6(CHCI,) =7.27; 13CN M R :
62.9MHz. 2-4. CDCI,. 25'C. 6(CDCI,) =77.0, 5 : CD,CN. 25 C,
d(CD,CN) = 1.30; "B N M R : 25.52 MHz, CDCI,, 25 'C.BF, . OEt, external:
I9F NMR: 84.67 MHz, CDCI,, 25°C. CFCI,.
Dedicated to Professor Dietrich Mootz
on [he occasion oj'his 60th birthday
The electron-withdrawing effect of the CF, groups is responsible for the reactivity of the BN bond of (dimethylamino)bis(trifluoromethyl)borane (l),which is significantly
different from that of other aminoboranes.['l Compound 1,
like other aminoboranes, adds H-acid compounds such as
hydrogen halides and H,0;[21 furthermore, like isosteric
alkenes, 1 is capable of [2 21 cycloadditions with isocyanates and isothiocyanate~,[~I
[2 41 cycloadditions with
dienes and en one^,[^] and ene reactions with carbonyl compounds and nit rile^.[^] Consequently. it was also to be expected that 1 would react with carbenes and thus, we investigated its reaction with diazomethane and two derivatives.
We found that 1 reacts readily with diazoalkanes
R1R2C=N=N to give the novel azoniaboratacyclopropanes
2-4 in high yields.
+
+
R' R 2
a o
(CF,),B=NMe,
1
\i
L
p.
+ R i R 2 C = & N ..
(d. 16.6 Hz. l H ; C H , ) 3.54 (d. 16.6 Hz, lH;CH,),7.20-7.33 ( m , 5 H ; C 6 H , ) ;
I 3 C / l H ) N M R : 6 = 2.64 (q, 5J(C,F) =1.9 Hz), 34.65 (4, 4J(C,F) = 2.1 Hz),
43.27 (4. '4C.F) = 2.4Hz). 47.94 (q. &J(C,F)= 2.8 Hz), -50.5 (broad),
126.4(~), 128.1(s), 128.6(~),138.l(~);"B NMR. 6 = -14.2(s); I9F N M R :
6 = - 55.7(s). -56.l(s); IR (KBr): i.[cm-l] =1100, 1076 (C-F).
5 . 'H N M R : 6 =1.31 (t. '4H.H) =7.1 HL, 3 H ; CH,), 2.78 (d, 3J(H,H) =
5 . 6 H ~ .6H.CH,). 4.22 (4. 3J(H.H) =7.1 Hr. 2 H ; CH,), 7.18 ((broad), 1 H :
NH); "C('H] N M R : 6 =14.69(s). 40.50 (sept. &J(C.F) = 1 4 Hz). -44.9
(broad). 62.06(s). 133.18 (4.4 'J(C.F) = 306 Hz, 'J(C.Bj =78 Hz), 172.04 (s);
"B N M R : 6 = - 8 . 4 ( ~ ) ;I9F N M R : 6 = - 63.8 (4, 'J(B.F) - 3 3 Hz): IR
(KBr): i.[cm-'] = 2100. ( C = N = N ) ; 1650, (C=O): 1091. (C-F).
corresponding angles in the three-membered ring, but, as a
result of steric interactions between the B and C substituents,
are twisted by 9.5(5)" and 8.3(5)", respectively, in the direction of the NMe, group. This strain has different effects on
the distances in the three-membered ring. Whereas the N-C
bond is 0.08(1) 8, longer than the average N-CH, distance,
the B-C bond (1.595(5) 8,))is as yet the shortest in a ring
system containing (CF,),B (cf. B-CH, in 1,1,4,5-tetramethyl-2,2-bis( trifluoromethy1)-I -azonia-2-borata-4-cyclohexene: 1.599(3)
The similarity of the lengths of different bonds in the three-membered ring is remarkable, as is the
fact that the Si-C bond is 0.072(7) 8, longer than the average
Si-CH, distance.
Ethyl diazoacetate, in contrast, reacts in an entirely different way with 1. The borylated ethyl diazoacetate 5 is formed
at - 120 "C in almost quantitative yield. Compound 5 is as
//
+
-N,
(CF j B-NMe,
32Q
0
2. R 1 = R 2 = H
3, R ' = H, R 2 = SiMe,
4. R ' = CH,Ph, R 2 = SiMe,
The products 2-4 are sublimable and stable up to about
90 "C. Their constitution was derived from the N M R spectra
(Table 1). We carried out an X-ray crystal structure investigation for 4.[61This shows (Fig. 1) that the B-N bond in the
three-membered ring is the shortest found so far between
tetracoordinated boron and nitrogen atoms.[41Several short
contacts occur between the ring substituents; as a result the
exocyclic valency angles are below the tetrahedral value, despite the small angles in the three-membered ring. The substituent planes B,C(l),C(2) and C,C(S),Si d o not bisect the
[*I
[**I
384
Prof. Dr. H. Burger. DipLChem. A . Ansorge. Prof. Dr. D. J. Brauer,
Dipl.-Chem. T. Hagen. Dr. G . Pawelke
Anorganische Chemie, FB 9 der Universitit-Gesamthochschule
Postfach 100127 D-W-5600 Wuppertal 1 (FRG)
This work was supported by the Minicterium fur Wissenschaft und
Forschung Nordrhein-Weslfalen and the Fonds der Chemischen Industrie.
G
VCH Verlugsge.\rllschufl mbH, W-6940 Weinherm.1993
Fig. 1. Crystal structure o f 4 (in perspective). Selected distances [A] and angles
I"]with standard deviations in parentheses: B-C 1.595(5), B-N 1.560(5). B-C(I j
1.614(6), B-C(2) I .609(6),C-N 1.567(4),C-C(5) 1.540(5), C-Si 1.941(3), N-C(3)
1.493(4). N-C(4j 1.477(4); C-B-N 59.2(2). C(I)-B-C(2) 107.9(3). B-C-N 59.1(2),
C(S)-C-Si 108.3(2). B-N-C 61 3(2). C(3)-N-C(4) 107.8(3)
0570-0~33/93/0303-0384
S; 10.00
+ 2510
Angr~c..Chem.In1
Ed Engl. 1993, 32. N o . 3
thermally stable as diazoacetate itself and melts at 84°C
without decomposition. The constitution of 5 is deduced
'0:
Et-0-C
(CF,),B=RMe,
+ N,CHCO,Et
+
1
//
\
8 " .
C=N=N
/
5
(CFJ,B\o
NHMe,
from the IR and N M R spectra as well as from an X-ray
structure analysis.['] The latter shows (Fig. 2) that the
ethoxycarbonyldiazomethane group including the B atom is
planar within k0.06 A. This planarity and the short C(3)C(4) bond length (1.441 A) are characteristic for a delocalized n-electron system in this part of the molecule. The BC(3) distance is normal.r71Noteworthy is the intramolecular
hydrogen bonding.
pentane (15 inL). at -10°C. 2. 3: The reaction mixture was stirred for 1 h at
room temperature and subsequently condensed in a high vacuum fractionating
apparatus. Compounds 2 and 3 were frozen out in a trap at - 10 C . 4: The
reaction mixture was stirred for 1 h at room temperature and subsequently the
solvent was removed under vacuum. Compound 4 was isolated from the remaining black residue by sublimation a t 40"C in a high vacuum apparatus and
recrystallized from CH,Cl,/petroleum ether
5: Ethyl Diazoacetate (1 1 .O mmol) was added dropwise to 1 (2.0 g. 10.3 mmol).
dissolved in dry CH,CI, (15 mL). at - 1 2 0 . The solvent was removed under
vacuum while the reaction mixture was warmed from - 70°C lo room temperature. and the residue recrystallized from acetonejpetroleum ether. Yields/rn.p.:
2: 9 5 % ; 3 0 ' C ; 3 - 9 7 % / 3 5 " C ; 4 56%:74 C;5: 98%:84 'C. Spectroscopicdata
of 2-5 are given in Table 1.
Received: October 22, 1992 [Z 5637 IE]
German version: A n g w . Chwn. 1993, 105, 429
[I] R. Koster, in Merhoden Org. Chem. ( H o u h i w W q l ) 4rh. Ed. 1952
(Organobori'ErbindungenjVol. 13/3a/3b/3c, Thieme. Stuttgdrt. 1982, 1983
and 1984.
[2] D. J. Brauer. H. Burger, F. Dorrenbach. G. Pawelke, W. Weuter, J.
Orgununwr. Cheni. 1989, 378, 125-137.
131 A. Ansorge, D. J. Brauer. H. Burger, F. Dorrenbach, T. Hagen. G.
Pawelke, W. Weuter, J Urgunurner. Chem. 1991, 407. 283-300.
[4] A. Ansorge, D. J. Brauer, H. Burger, F. Dorrenbdch, T. Hagen, G.
Pawelke, W. Weuter, J Orgunomer. Cl7em. 1990,396, 253 267.
[5] A. Ansorge. D. J. Brauer, H. Burger, T. Hagen. G. Pawelke. J. Orgunomer.
Chem., i n press.
161 a) Single crystals of 4 were obtained from dichloromethaneipetroleurn
ether: u =7.396(3), h = 10.840(4), c = 12.277(6) A, 1 = 92.93(3), =
95.66(4). 7 = 10X.71(3)", V = 924.1(7) A', 2 = 2. pIalrd
= 1.327 gcm-', Pi
(no. 2); T = 299 K ; measurement range 3 " 1 2 0 < 5 0 '; Mo,,: 3249 independent reflections. R = 0.055 for 2185 observed reflections (cl24u(F0))
and 246 parameters. R , = 0.068 ( w = l/(uz(Fo)+ 0.0003 FS). b) Further
details of the crystal structure investigation may be obtained from the
Fachinformationszentrum Karlsruhe, Gesellschaft fur wissenschaftlichtechnische Information mbH, D-W-7514 Eggenstein-Leopoldshafen 2
(FRG) on quoting the depository number CSD-56793. the names of the
authors, and the journal citation.
171 See also A. Ansorge, D. J. Brauer, H. Burger. F. Dorrenbach, B. Krumm,
G. Pawelke, Z. Nuturjursch. B 1992, 47. 772-782.
[8] Single crystals of 5 were obtained from acetone/petroleum ether:
u = 15.125(2). b = 12.678(1), c = 14.406(3) A, V = 2762.5(7) A', Z = 8,
pca,Ld
=1.476gcm--', Phcn (no. 60); T = 300 K ; measurement range
5 " < 2 6 < 5 0 " ; Mo,,; 2427 independent reflections, R = 0.053 for 1557
observed reflections (F0t40(F,)) and 198 parameters, R , = 0.052 (M.= 11
(uZ(FO) 0.0002F.3. See also [6b].
[9] R. Boese. P. Paetzold. A. Tapper, Chern. Ber. 1987, 120. 1069-1071; A.
Tapper, T. Schmitz, P. Paetzold. ibid. 1989. 122, 595-601; B. Glaser, H.
Noth, ihid. 1985. 97,424-425; M. Arthur, A. Bdceiredo. G. Bertrand, J.
A m . Chem. Sor. 1991, 113. 5856-5857.
[lo] H. S. Turner, Chem. fnd. (Londonj 1958, 1405; J. Goubeau. K. H. Rohwedder, Justus Liehigs Ann. Chem. 1957, 604, 168- 178.
~
Fig. 2. Crystal structure of 5 (in perspective). Selected distances [A] and angles
with standard deviations in parentheses: B-N(3) 1.612(4), B-C(1) 1.615(5),
B-C(2) 1.624(5). B-C(3) 1.608(4), C(3)-C(4) 1.441(4), C(3)-N(1) 1.321(4), N(1)N(2) 1.123(3),C(4)-0(1) 1.217(3), C(4)-O(2) 1.341(3), H(N)-O(1) 2.18(3); C(3)B-N(3) 107.0(2), C(1)-B-C(2) 109.0(3). B-C(3)-C(4) 124.6(3), B-C(3)-N(1)
120.2(3). C(4)-C(3)-N(l) 115.0(2), C(3)-N(l)-N(2) 178.6(3), N(3)-H(N)-O(l)
141(3).
[;I
The azoniaboratacyclopropanes 2-4 are the first BNC
three-membered rings in which boron and nitrogen occur
with the coordination number four. Thus, they are the first
BN isosteres of cyclopropane, whereas the corresponding
isosteres of the cyclopropene have been known for some
time.['] The cyclopropanation of the B-N double bond is
unprecedented, since with diazomethanes, boranes usually
insert CH, into the b o r o n 4 e m e n t bonds with retention of
the coordination number three for the boron atom.['01 The
inductive effect of the two trifluoromethyl groups makes a
boron atom so electronically poor that it strives for saturation by increasing its coordination number to four. The reaction that I undergoes with ethyl diazoacetate follows the
same principle and corresponds to the known reaction with
carbonyl compounds R1CH,COR2, during which dimethylamino-stabilized bis(trifluoromethy1)boranes of the type
(CF,),B(R'CHCOR').HNMe,
are formed.''] In contrast,
borylated diazomethane derivatives with boron with the coordination number three are well known.[']
Experimental Procedure
2-4: An ethereal solution of diazomethane (1 1.8 rnrnol). trimethylsilyldiazornethane, or benzyl(trirnethylsilyI)diazomethdne (for the synthesis of 2, 3,
and 4, respectively) was added dropwise to 1 (2.0 g, 10.3 mmol), dissolved in dry
Angeu,. C%Pm Inr. Ed. E n d . 1993. 32. Nu. 3
0 VCH
+
Stereochemistry of Norbornyl + Norpinyl
Rearrangements
By Wolfgang Kirmse* and Dirk Minkner
The ionization of exo-2-norbornyl derivatives I b occurs
with the participation of the C1 -C6 bond (1 b + 3)."] For
endo-2-norbornyl derivatives 1 a corresponding participation of the C1 -C7 bond (1 a + 4) should likewise be possible. However, the ring strain thereby increases,r21so that
the k, process 1 a + 2 + 3 is often preferred over the k, route
1 a + 4131 (Scheme 1). Charge destabilizing groups at C3[41
or C2, and similarly, charge stabilizing groups at C1['] or
C6@] can cause (partial) rearrangement to give norpinyl
derivatives, particularly when nitrogen (X = N:) serves as
the leaving group. To date it remains unclear whether the
[*I
Prof. Dr. W. Kirrnse. Dip1.-Chern. D. Minkner
Fakultit fur Chemie der Universitit
Postfach 102148. D-W-4630 Bochum (FRG)
VerlagsgesellschafimbH, W-6940 Weinheim, 1993
0570-0833/93~0303-0385
$ 10.00t.25jO
385
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borylated, diazoester, bnc, compounds, dimethylamino, cyclopropane, trifluoromethyl, isosteres, bis, diaz, boranes
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