WILLIAMS and HAMILTON prepared di-n-+lphosphine oxides, but were unable t o isolate any diarylphosphine oxides (e.g., diphenylphosphine oxide).l We have succeeded in preparing diphenylphosphine oxide (I) b y the action of phenylmagnesium bromide on diethyl hydrogen phosphite : (EtO)*PH(:O) --+ Ph,P(:O)-MgBr ---W-Ph,PH(:O) (I)We have shown that diphenylphosphine oxide is in equilibrium with diphenylphosphinous acid (11). Infrared measurements indicate that under normal conditions the phosphine oxide form (I) preponderates. However the aqueous solution reacts quantitatively with silver nitrate solution t o give silver diphenylphosphinite : this reaction is not instantaneous. Diphenylphosphine oxide was oxidised quantitatively in aqueous solution b y bromine yielding diphenylphosphinic acid (111), also produced b y dilute hydrogen peroxide solution or acidified potassium permanganate solution.
When 5.1 g. of I was redistilled after having been stored at 0°for 3 months, 4.9 g. (96%) of I, b.p. 69-71.5°was obtained and 0.1 g. of residue (2%) was left.Adduct of I with maleic anhydride. To 0.98 g. (0.01 mole) of maleic anhydride dissolved in 20 ml. of ether contained in a 125-ml. Erlenmeyer flask was added 0.94 g. (0.01 mole) of I. No heat was evolved and no precipitate formed on standing overnight at room temperature; however, when the solution was cooled in a refrigerator, the adduct crystallized as white needles, 1.90 g. (99%), m.p. 91-92°( petroleum ether, b.p. 30-40°).
Die Reformatsky-Reaktion zwischen Cyclohexenoxyd und Bromessigester wurde erneut untersucht und die Ausbeute an P-Hydroxy-P-cyclopentyl-propionsaure-athylester (I) verbessert. Fur die Ringverengung wird ein Reaktionsmechanismus vorgeschlagen. I spaltet mit Phosphoroxychlorid in Pyridin Wasser ab zum 6-Cyclopentyl-acrylsaureester, der bei der Michael-Addition mit Acetessigester 4-Carbathoxy-5-cyclopentyl-cyclohexandion-(l.3) ergibt. 5-SubstituierteResorcine werden bequem iiber die entsprechenden 5-substituierten Dihydroresorcine (Cyclohexandione-( 1.3)) erhalten, die im allgemeinen entweder durch Michael-Addition eines a-Diesters an ein a.P-ungesattigtes Keton') oder eines P-Ketoesters an einen =.a-ungesattigten Ester % 3 ) und anschlieBende Dieckmann-Cyclisierung der Addukte hergestellt werden.
The reaction of 4-[(5'-chloro-3',6'-diniethyl-2'-benzofur~yl)methylene]-2-phenyloxazolin-5-one with hydrazine hydrate gives a-benzamido-/3-(5-chloro-3,6-dimethyl-2-benzofuryl)acrylohydrazide which is converted to the corresponding azide by nitrous acid. On heating in benzene, the azide yields 4-[(5'-chloro-3',6'-dimethyl-2'-benzofuranyl)methyl]-2H-6-phenyl-1,3,5-oxadiazin-2-one the hydrolysis of which furnishes 5-chloro-3,6-dimethyI-2-benzofurylacetic acid.In connection with a project under way in this laboratory on the synthesis of analogues of usnolic acid, a few 2-benzofurylacetic acids were required. 2-Benzofurylacetic acids were previously 1 prepared from 2-formylbenzofurans by the hydrolysis of the derived azlactones to pyruvic acids and oxidation of the latter by alkaline hydrogen peroxide. It has, however, been observed by us during the synthesis of some usnolic acid analogues that the azlactones of a few 2-formylbenzofurans offer hindrance to hydrolysis, which sometimes results only in tars. Moreover the derived pyruvic acids in some cases are so sensitive to oxidation by alkaline hydrogen peroxide that the reaction is hard to control and sometimes furnishes sticky intractable gums. We, therefore, became interested in the reaction explored by Jennings 2 for the conversion of m-nitrobenzaldehyde to m-nitrophenylacetic acid. The method involves the conversion of the azlactone of the aldehyde to the hydrazide which furnishes the azide with nitrous acid. On heating in benzene the azide undergoes Curtius rearrangement to yield an oxadiazine the hydrolysis of which gives m-nitrophenylacetic acid.In the present investigation this reaction has been applied to the preparation of 5-chloro-3,6-dimethyl-2-benzofurylacetic acid. Starting from 5-chloro-2-hydroxy-4-methylacetophenone 3, 2-acetyl-4-chloro-5-methylphenoxyacetic acid (11, R=H) was prepared and converted into 5-chloro-3,6-dimethylbenzofuran (I, R=H), which by Gattermann's method yielded
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