Zur Reaktion von Dialkylphosphiten mit α‐Enonen, II. 2:1‐Addukte aus Dimethylphosphit und α‐Enonen: Darstellung von (1‐Hydroxy‐1,3‐alkandiyl)diphosphonaten und 5‐Dimethoxyphosphoryl‐2‐methoxy‐1,2‐oxaphospholan‐P‐oxiden

Reaction of Dialkyl Phosphites with α‐Enones, II. – 2:1 Adducts from Dimethyl Phosphite and α‐Enones: Synthesis of (1‐Hydroxy‐1,3‐alkanediyl)diphosphonates and 5‐Dimethoxyphosphoryl‐2‐methoxy‐1,2‐oxaphospholane P‐Oxides On NaOCH3‐catalyzed reaction with two equivalents of dimethyl phosphite (2), various α‐enones 1 are transformed into the diphosphonates 5 (e.g. 5a, 5b, 5e, 5f), which, depending on the structure of the enone, can further react with ring closure to give the 1,2‐oxaphospholanes 6 (e.g. 6c, 6g, 6h), or with phosphonate‐phosphate rearrangement of the α‐hydroxyphosphonate moiety to yield compounds 7 (e.g. 7d). The formation of the 2:1 adducts is believed to occur via addition of 2 to the carbonyl group of the (3‐oxoalkyl)phosphonates 4, formed from thermodynamically controlled 1,4 addition of 2 to 1. Compounds 4 could also be treated with 2 to yield 2:1 adducts (e.g. 4c → 5c, 4d → 5d, 4d → 7d).