F'ropargyl ethers HCECCHaOR [R = alkyl or -CH(CHa)(OCaHa)] have been isomerized with good yields into the corresponding allenyl ethers CHa=C=CHOR by warming with potassium rert.-butoxide at 70 '.These allenyl ethers can be metallated with butyllithium in ether or alkali amides in liquid ammonia. In ether, subsequent alkylation with alkyl halides R'Hal affords a-substituted allenyl ethers CHs=C=C(R)OR. Alkylation in liquid ammonia produces a mixture of this same compound and the y-substituted product R'CH=C=CHOR. In both cases reasonable yields are obtained. Sodamide and potassium amide quickly convert allenyl ethers CH2=C=CHOR into metallated propargyl ethers MCEC-CHsOR (M = Na or K). If alkylation is not performed almost simultaneously with the metallation with sodamide or potassium amide, the only alkylation product obtained is R'CE CCHzOR.

Metallation of methoxypropadiene, CH2-C =CHOCHa, with butyllithium in ether, followed by reaction with carbonyl coniponnds, R'RZC=O (R1 and R2 ~= H or alkyl or R1R2C = cyclohexyl), affords carbinols, CH2=C-C[CR1R2 (OH)]OCH3, in excellent yields. Acid-catalysed hydrolysis of these carbinols gives nearly quantitative yields of unsaturated ketols, Acid-catalysed addition of alcohols, ROH (R = CH3 or CzHs), to methoxypropadiene affords acrolein acetals, CHZ = CHCH(OCH3) (OR) Diels-Alder addition of ethoxypropadiene to a,/?-unsaturated aldehydes, R3CH = CH -CH = 0 (R3 := H or CHs), leads to derivatives of 2,3-dihydropyran (VIII).

l‐Alkoxy‐l‐(α‐hydroxyalkyl)allenes R1CH=C=C(OR2)C(OH)R3R4 (Ia) have been converted with high yields into 3‐alkoxy‐2,5‐dihydrofurans (II) using potassium tert‐butoxide in dimethyl sulfoxide. Hydrolysis of II with dilute sulfuric acid afforded 3‐oxotetrahydrofuran derivatives III. l‐(β‐Hydroxyalkyl)‐l‐methylthioallenes R1CH=C=C(SCH3)CH2CH2OH (IVb) and the analogous oxygen compounds IVa yielded 2‐alkyl‐3‐methylthio‐4,5‐dihydrofurans (Vb) and a mixture of 3‐methoxy‐2‐methyl‐4,5‐dihydrofurans (Va) and 3‐methoxy‐2‐methylenetetrahydrofuran VI, respectively. The preparation of the hydroxyallenes is described.

Abstract. Reductive cleavage of the sp3 carbon-sulfur bond in alkyl-or aryl-substituted 2-mercaptoor 2-amino-6H-l,3-thiazines with sodium in liquid ammonia affords almost quantitative yields of the sodium salts of 1 -alkenyl-dithiocarbamates and -thiourea, respectively. The dithiocarbamates can be converted into I-alkenyl isothiocyanates by reaction with chloroformates and subsequent pyrolysis to give overall yields of 54-88S:;. Cis-trans isomerization of the 1 -alkenyl isothiocyanates can only be achieved by irradiation.

Abstract. The course of the reductive ring-opening reactions of 2-mercapto-, 2-hydroxy, 2-amino-, '-methylamino-and 2-dimethylamino-4-methylthiazoles with sodium in liquid ammonia, yielding substituted propenethiolates. has been found to depend on the nature of the hetero substituent. The mechanism of the ring opening is discussed.