Convenient synthesis of 1‐alkoxy‐1,2‐dihydrophosphinine 1‐oxides by ring enlargement

Abstract

The addition of dichlorocarbene to the double bond of I -alkoxy-dihydrophosphole oxides and subsequent thermolysis of the adduct so obtained affords mixtures of the two double bond isomers of alkoxy-dihydrophosphinine oxides, i f the latter step is carried out in the presence of triethylamine. Experimental data support the involvement of a cationic intermediate during the opening of the cyclopropane ring. A simplified procedure for the preparation of the starting dihydrophospholes is also presented.

Unexpected condensation reaction of two units of 1,2‐dihydrophosphinine 1‐oxides in the presence of tetracyanoethylene

“…ring opening of 3-phosphabicyclo[3.1.0]hexane 3-oxide (1), was used as the starting material (Scheme 1) [10][11][12].…”

“…Mass spectrometry was performed on a ZAB-2SEQ instrument. The starting dihydrophosphinine oxides were prepared as described earlier [10][11][12].…”

Alkylating esterification of 1‐hydroxy‐3‐phospholene oxides under solventless MW conditions

“…The method is also applicable for the synthesis of cyclic phosphinates, such as 1-alkoxyphospholene 1-oxides (3) involving the hydroxyphospholene oxide (2) as the starting material and the chlorophospholene oxide (4) as the intermediate (Scheme 1) [3,4]. The alkoxyphospholene oxides (3) can also be obtained directly by the alcoholysis of the phospholium salts (1) [5][6][7] available from the McCormack cycloaddition of a variety of dienes with phosphorus tribromide. According to a recent method developed by the Keglevich group, the hydroxyphospholene oxides can be directly esterified by alcohols under solventless MW conditions [8].…”

Synthesis of 1,2,3,4,5,6-Hexahydrophosphinine 1-Oxides by Catalytic Hydrogenation of 3-Phosphabicyclo[3.1.0]hexane 3-Oxides

“…6,6-Dichloro-3-phosphabicyclo[3.1.0]hexanes (1) easily available from 3-phospholene 1-oxides by the addition of dichlorocarbene to the double bond [1,2] are useful intermediates for the preparation of 1,2,3,4,5,6-hexahydrophosphinine 1-oxides (3). In the first method, the dichlorocarbene adducts (1) were transformed to the isomeric mixtures (A) and (B) of the dihydrophosphinine oxides (2) by thermolysis [2], that were then hydrogenated catalytically to give hexahydrophosphinine oxides (3) [3] (Scheme 1).…”

“…In the first method, the dichlorocarbene adducts (1) were transformed to the isomeric mixtures (A) and (B) of the dihydrophosphinine oxides (2) by thermolysis [2], that were then hydrogenated catalytically to give hexahydrophosphinine oxides (3) [3] (Scheme 1).…”