Vinyl Ethers Containing an Epoxy Group: XXIII. Reactions of Alkynylmagnesium Bromides with Glycidol Ethers: Synthesis and Thermal Transformations of 1-[2-( Vinyloxy)ethoxy]- and 1-(Allyloxy)-5-hexyn-2-ols, -5-phenyl-4-pentyn-2-ols, and -3-bromo-2-propanols

Abstract

Reaction of 2-[2-(vinyloxy)ethoxy]methyl-and 2-(allyloxymethyl)oxiranes with 2-propynyl-and phenylethynylmagnesium bromides (1055°C, 0.54 h) resulted in new representatives of the series of 1-organyloxy-5-hexyn-2-ols, -5-phenyl-4-pentyn-2-ols, and -3-bromo-2-propanols in 5099% yields. During distillation the 1-[2-(vinyloxy)ethoxy]-5-phenyl-4-pentyn-2-ol and -3-bromo-2-propanol transform respectively into 2-methyl-4-(3-phenyl-2-propynyl)-and 2-methyl-4-(bromomethyl)-1,3,6-trioxocanes via intramolecular cyclization involving the hydroxy and vinyloxy groups.The reaction of organomagnesium compounds (Grignard [2, 3] and Iotsich reagents [3,4]) with oxiranes is a classical building up method of alcohol synthesis (with formation of a CC bond) [3, 511], also used for acetylene and allene alcohols [611]. The best studied reaction is that of the Grignard reagents with the simplest epoxides: unsubstituted oxirane, methyl-, phenyl-, 2,2-dimethyl-, and 2,3-dimethyloxiranes, although other examples of this process are also described (with naturally occurring epoxides, epoxyalcohols, epoxyketones, epoxyesters, diepoxides etc.) [511]. The reaction finds an industrial application in production of various technically important alcohols, in particular, those used in fragrance industry: 2-phenyl-1-ethanol (rose oil) [12], 3-phenyl-1-propanol (with the hyacinth fragrance) [13], 3,7-dimethyl-6-octen-1-ol (rhodinol) with a rose scent [14], alcohols with the properties of sex attractants and plant growth regulators. [15].The preparation was reported of chiral homoallyl alcohols in reaction of vinylmagnesium halides with glycidol derivatives containing as protection functions benzyl, methoxtphenylmethyl, tert-butyldimethylsilyl, and tertbutyldiphenylsilyl groups [16]. (R)-1-(Benzyloxy)-5-hexen-2-ol, the key intermediate in the stereoselective synthesis of trans-2,5-dioxymethylpyrrolidone derivatives possessing C 2 -symmetry, was obtained by treating with allylmagnesium chloride the optically active (S)-2-[(benzyloxy)methyl]oxirane [17]; reactions were performed of 2-(methoxymethyl)-and 2-(phenoxymethyl)-oxiranes with ethyl-and phenylmagnesium bromides [18]. Alkynols and allenols originate from both reactions of alkynylmagnesium halides with oxiranes [610] and of 2-ethynyloxiranes with Grignard reagents 11]. The alkynols combining the properties of the three most important classes of organic compounds (alcohols [19], acetylenes [20], and CH-acids when the compounds contained fragments CºCH and/or CH 2 CºC [21,22]) are valuable intermediates in preparation of a lot of synthetically and commercially significant products (chemicals for agriculture, drugs, and fragrant substances [9,23]). They are widely used in the synthesis of functionalized acetylene alcohols and diols [1, 24], heterocycles, including derivatives of furan [25], pyran [26], pyrrole [27], indole [28], pyrazole [29], 2,3-dihydropyridine, pyridine [30], benzazepine-1,5-dione [31], thiophene [32], various allene systems [20, 23, 24, 33], in particular, allenols that ar...