Skipped diynes. V. Secondary diethynyl carbinols. Base-catalyzed ynol to enol rearrangements and ultraviolet spectra and conjugation

Abstract

Bis(l-propynyl)methanol (la), bis(phenylethynyl)methanol (lb), and tetrakis( l-propynyl)ethane-l, 2-diol (10) are highly activated propar gyl alcohols. Because of their sensitivity to acid, conversions of 1 to carbamate, ester, ether, and halide best proceed under neutral or basic conditions. Even so, disruptions of the diyne system are common, e.g., the formation of 4-bromo-2,5-heptadiyne and 2-bromo-2,3-heptadien-5-yne from la, thermal cleavage of 10, and a base-catalyzed ynol to enone rearrangement of lb to l,5-diphenylpent-l-en-4-yn-3-one ( 14). It is shown that the conversion of 1,3-diphenylpropynol (15) to 1,3-diphenylpropenone ( 16) in the presence of base is another example of this rearrangement and that reactions which appear to be characteristic of the ynol (lb, 15) are probably those of the enone (14,16). The question of conjugation in skipped 1,4-diynes is discussed in the context of the uv spectra of several series and it is concluded that, in the diethynylmethanes, -carbinols, and ketones, the central function at the 3 carbon does transmit conjugation. The trialkylethynylcarbinols are anomalous in that their uv absorption bands are decidedly hypsochromic relative to all members of the diethynyl families.

Fe(III)-Lipoxygenase Converts Its Suicide-Type Inhibitor Octadeca-9,12-diynoic Acid into 11-Oxooctadeca-9,12-diynoic Acid

“…The UV spectrum of P1 strongly resembles that of tetradeca-5,8-diyn-7-one, which has absorption maxima at 240 and 250 nm, with relative intensities of 1.02:l.OO and an €250 of 1.17 x 104 mol-'*Lcm-' in methanol. Similar values were reported for trideca-5,8-diyn-7-one, which has absorption maxima at 239.5 and 250 nm, with relative intensities of 1.01: 1.00 and an €250 of 1.33 x lo4 mol-'*L*cm-', when measured in ethanol (Metler et al, 1968;Migliorese et al, 1974).…”

Comparison of the bis(ferrocenylethynyl)phenylmethylium cation with bis(ferrocenylethenyl)methylium analogues

“…Related AC"CCRC"CAbridged cations with the Cp(PR 3 ) 2 RuA end group have been reported; these have been shown to be symmetrical in solution on the NMR timescale and, in one case, in the solid state by X-ray crystallography [16]. Several reactions of (PhCC) 2 CHOH under acid conditions, including conversion to PhC"CCH@C@ CPhBr and PhC"CCH@CHC(O)Ph, presumably involve [(PhCC) 2 CH] + as an intermediate [17]. However, attempts to isolate cations such as [(4-Me 2 NC 6 H 4 CC) 2 CR] + (R = Ar, CCAr) from treatment of the corresponding alcohol with perchloric acid gave the cyclised pyrylium species [18].…”

Incorporating Phosphaalkenes into Oligoacetylenes

“…We envisaged that APAs would be accessible through a sequence of three steps from commercially available acetylenes and ethyl formate (Scheme ). In the preparation of carbinols 1 a – d 18 it is important that the reaction times are kept short and the temperature below room temperature to avoid the previously described base‐catalyzed ynol‐to‐enone rearrangement 19. Treatment of etheric solutions of the carbinols with thionyl chloride affords the 3‐chloropenta‐1,4‐diynes 2 a – d in acceptable yields 20.…”