Facile Reduction of Aromatic Aldehydes, Ketones, Diketones and Oxo Aldehydes to Alcohols by an Aqueous TiCl3/NH3 System: Selectivity and Scope

Abstract

A simple and rapid procedure for the almost quantitative reduction of aromatic aldehydes, ketones, diketones and oxo aldehydes to alcohols by use of TiCl 3 /NH 3 in aqueous methanol solution is reported. The reducing system distinguishes between different classes of aldehydes and/or ketones, and many functionalities that usually do not survive under reducing conditions are tolerated well. The concept of reversal

Hydrogenation of Cyclic 1,3-Diones to Their 1,3-Diols Using Heterogeneous Catalysts: Toward a Facile, Robust, Scalable, and Potentially Bio-Based Route

“…Through isolation by column chromatography, indane-1,3-diol ( 8b ) was obtained in a 68:32 cis – trans ratio. However, the isolated product from a third experiment was allowed to crystallize from refluxing ethyl acetate, as reported by Clerici et al , leading to the facile isolation of cis -indane-1,3-diol ( 8b-cis ) in 99% purity.…”

Titanium(III) Trichloride

“…The protocol is tolerant to a number of functional groups, such as acids, esters, amides and cyano, bromo, chloro, methoxy, dimethyl acetal and α-cyclopropyl groups. 16 aqueous TiCl 3 Lee and co-workers found that 2-methoxy-6-methyl- [1,4]benzoquinone can be reduced to 2-methoxy-6-methylbenzene-1,4-diol using TiCl 3 with high yield. 17 (E) Arylations of Heterocycles: Pratsch et al reported that titanium-mediated arylations led to the formation of C-C bonds by radical reactions of hydroxy phenyldiazoniumion ions and a highly reactive arylradical scavenger, such as furan and pyridine.…”

“…8 In addition, the aqueous TiCl 3 /NH 3 system has been used to promote the reduction of aromatic aldehydes, ketenes, and diketones to give alcohols. 9,10 Reductive cyclizations of oxoamides to produce indoles can also be effectively promoted by TiCl 3 .…”

“…8 In addition, the aqueous TiCl 3 /NH 3 system has been used to promote the reduction of aromatic alde-hydes, ketenes, and diketones to give alcohols. 9,10 Reductive cyclizations of oxoamides to produce indoles can also be effectively promoted by TiCl 3 . 11 Apart from these applications, TiCl 3 is also known as a Lewis acid to catalyze the SnCl 2 -mediated Barbier reactions between aldehydes and allyl halides in aqueous media.…”

Highly atom-efficient and chemoselective reduction of ketones in the presence of aldehydes using heterogeneous catalysts

“…3 To date, several similar approaches have been proposed. [4][5][6][7][8][9] However, these methods have the fatal problem of low atom efficiency due to the necessity of stoichiometric protecting reagents, metal hydrides, and toxic acids for the deprotection, producing large amounts of waste (Fig. 1a).…”