Zur Chemie der 1,3,5-Triaza-2-phosphorinan-4,6-dione. Teil VII+. Über die Synthese von 2-Methoxy- und 2-Trimethylsiloxy-1,3,5-trimethyI- 1.3.5-triaza-2λ3-phosphorinan-4,6-dion sowie 2-Chlor-1,3,5-trimethyl- 1.3.5-triaza-2-oxo-2λ4-phosphorinan-4,6-dion / Chemistry of the 1,3,5-Triaza-2-phosphorinane-4,6-diones. Part VII. Synthesis of 2-Methoxy- and 2-Trimethylsiloxy-1,3,5-trimethyl-1.3.5-triaza-2λ3-phosphorinane-4,6-dione and 2-Chloro-1,3,5-trimethyl- 1.3.5-triaza-2-oxo-2λ4-phosphorinane-4,6-dione