Issue in Honor of Prof. Jan Epsztajn ARKIVOC 2007 (vi) 193-216
to the corresponding diazo derivative 27 with a yield of 81% (Scheme 12).27 Subsequent catalytic hydrogenation of the latter compound using 10% palladium on charcoal in methanol gave the desired amination product 3a in a good yield.27
Diazo derivatives of diethoxyphosphorylacetates 27 were also used as precursors of rhodium carbenoids in N-H insertion reactions catalyzed by rhodium (II) acetate.32 A wide range of amines (R1 = aryl, R2 = H) and amides (R1 = acyl, R2 = H or alkyl) was used in this reaction to get the amination product in moderate to good yields.32-34 It should be noted, that both tosyl azide and diazo compound 27 are potentially explosive.32
OO
N3
EtO
1. Et3N / DMF EtO P
P
2. CF3SO2N3 EtO CO2R EtO CO2R 25 29
R = Et 40% yield H2 90% Pd / C
1. NaH / DME 2. Me O
NH2
EtO P
EtO CO2R
SO2N3
3a
H2 Pd / C
50 - 80%
N
R1 O
NR
1 R2 2O
R
N
EtO P+
N Rh2(OAc)4 / PhMe EtO
P _
EtO CO2R H N2 EtO CO2R
27 28
50 - 80% 32
88 - 93% 33, 34
Scheme 12
The amination of diethoxyphosphorylacetates can also be carried out via the azido derivative 29 (R = Et), which was obtained in the reaction of the corresponding starting compound 25 with trifluoromethanesulfonyl azide in a yield of 40%.35 Catalytic hydrogenation of the azide 29 gave the corresponding a-(diethoxyphosphoryl)glycinate 3a in a 90% yield (Scheme 12). 35
4.1.3. Formation of the Ca-P bond Several methods of synthesizing a-(diethoxyphosphoryl)glycinates by the formation of a Ca-P bond have also been described. One of them consists in the addition of diethyl phosphite to the ISSN 1424-6376 Page 203 ©ARKAT USA, Inc.
