Preparation of Substituted Oxaboroles from Sodium 1-Alkynyltrialkylborates and Acyl Chlorides.

0-sulfonic acid gave products of as yet unclarified structure.
The isothiazole structure (3) follows from the IR and UV
spectra and from elemental analyses.
( I ) , X=Y=CN
+ CI-NH2
-+
:aNH2
+
MCl
(3)
176
198
176
144
1,2-oxaboroles. Other possible products, such as methyl
ethyl ketone and diethylpropynylborane, could not be
detected.
A solution of 32 g (0.2 mole) of ( I ) in 60 ml of dichloromethane is added dropwise and slowly at 5-1OoC, with
cooling in ice-water, to 15.6 g (0.2 mole) of acetyl chloride.
A yellow color develops and sodium chloride separates.
Distillation of the filtrate gives, apart from the solvent, two
fractions. Fraction I (8.4 g, b.p. 32-33 'C/12 mm) contains
71 % of methyl propynyl ketone (gas-chromatographic analysis); fraction I1 (17.5 g, b.p. 68-69 "C/12 mm) is almost pure
(2.).
Benzoyl chloride and the salt ( I ) under the same conditions
afford 2,3,3,4-tetraalkylated 5-phenyl-2,3-dihydro-1,2-oxaborole (26) (b.p. 68 to 70 OC/lO-3 mm) in up to 30 % yield
together witn some phenyl propynyl ketone (6 %) and ethyl
phenyl ketone (7 %). The remainder consists almost wholly
of dark, tarry products.
The structure of the compound (2a) is proved by the mass
spectrum (molecular weight 180, one boron atom), the
infrared spectrum ( v c , ~ = 1690 cm-I), and the IH-NMR
spectrum [l CZHS(on B): z= 8.99 ppm; 2 CzHs (on C-3):
T C H ~= 8.6 ppm (quartet), T C H ~= 9.44 ppm (triplet); 1 CH3
(on C-4): T = 8.59 ppm; and 1 CH3 (on C-5): T = 8.07 ppm].
86
77
72
93
As a,P-amino nitriles the isothiazoles (3) can undergo
further reactions. For instance, when 0.01 mole of (3.) is
heated with 40 ml of a n equimolar mixture of ethyl orthoformate and acetic anhydridetsl on the water-bath for 3 hr,
evaporation affords the derivative (4). m.p. 76 "C, in 90 %
yield, which with a n excess of alcoholic ammonia at room
temperature gives compound (5), decomp. ca. 230 "C, in 85 %
yield. This is the first isothioazolo[3,4-d]pyrimidinereported.
H
(3)
(4)
Received: October 31st, 1966: revised: November 8th. 1966 [Z 367 IEI
German version: Angew. Chem. 79,56 (1967)
[*I Dr. K. Hartke and L. Peshkar B.Sc.
Institut fur Pharmazeutische Chemie und Lebensmittelchemie
der Universitat
Marbacher Weg 6
355 Marburg (Germany)
[**I We thank the Verband der Chemischen Industrie and the
Deutsche Forschungsgemeinschaft for financial support.
[l] For thioacylation of cyclopentadiene with trithiocarbonic
esters see K. Hartke, Tetrahedron Letters 1964, 2737; K. Hartke,
E. Schmidt, M . Castillo, and J. Bartulin, Chem. Ber. 99, 3268
(1966).
[Z] For condensation of acetophenone with 0-methyl thiobenzoate see E. Uhlemann and H. Miiller, Angew. Chem. 77, 172
(1965); Angew. Chem. internat. Edit. 4, 154 (1965).
[3] The yield of isothiazole from salts containing one nitrile
group is small.
[4]The chloramine solution was prepared at 0 "C from NaOH
20 g, water 100m1, ice l O O g , chlorine 14g, and 25% aqueous
NH3 8.5 g; the molar quantity stated refers to the NH3 content.
[ 5 ] E. C. Taylor and K. Hartke, J. Amer. chem. SOC.81, 2456
(1959).
The reaction can be extended to other sodium alkynyltrialkylborates; e.g. Na[(C3H7)3BC =C-CH3] and acetyl chloride
yield 4,5-dimethyl-2,3,3-tripropyl-2,3-dihydro-l,2-oxaborole,
with methyl propynyl ketone.
The substituted oxaboroles are sensitive to oxygen but are not
attacked by substances containing active protons (water,
ethanol, ethylene glycol) up to about 100°C. They d o not
form stable addition compounds with tertiary amines.
Like 1,2-diborylated alkenes, the compounds (2) are formed
probably by way of "borenylides" (3) 111. The ketones (4)
initially formed can be isolated only when trapped with
pyridine. The free compounds evidently rearrange readily to
(2).
( I ) + RCOCl
0 ,CH3
CZH5
'CO-R
-
(3)
Received: October 12th, 1966; revised November 4th. 1966 [Z 360 IEI
German version: Angew. Chem. 79,57 (1967)
[*I Dr. P. Binger
Max-Planck-Institut fur Kohlenforschung
Kaiser-Wilhelm-Platz 1
433 Miilheim (Germany)
[I] P. Binger and R . Koster, Tetrahedron Letters 1965, 1901.
Preparation of Substituted Oxaboroles from Sodium
1-Alkynyltrialkylboratesand Acyl Chlorides
Two New Syntheses of Arylhydrazines
By W. Burkhurdf and Th. Kuuffmann[*1
By P, Binger[*J
Sodium triethyl-1 -propynylborate and acetyl chloride give
only about 35% of methyl propynyl ketone and triethylborane, since about 50 % of the borate is converted into the
alkyl derivative (2a) of the hitherto unknown 2,3-dihydroR-CO-CsC-CH3
Na [( C2H5)3BC=C- CH3]
c2H5<,24
-N~CI- C~HS;B-C=C
+
RCOCl
Since a high temperature is required in the synthesis of
phenols or arylamines from arenesulfonates and alkali
hydroxides or alkali amides, it did not appear promising to
attempt a n analogous synthesis of arylhydrazines by means
+
B(CzH5)3
5-10°C
- NaCl
(1)
(a), R = CH3
84
Angew. Chem. internat. Edit. / Vol. 6 (1967) f No. I