US PATENT SUBCLASS 987 / 106
.~.~.~ Four-membered ring containing a single N atom is condensed or bridged to a carbocyclic ring system (9/568V)

Current as of: June, 1999
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987 /   HD   ORGANIC COMPOUNDS CONTAINING A Bi, Sb, As, OR P ATOM OR CONTAINING A METAL ATOM OF THE 6TH TO 8TH GROUP OF THE PERIODIC SYSTEM

30  DF  PHOSPHORUS COMPOUNDS (9/02; 9/06) {15}
49  DF  .~ Ring is devoid of a P or a metal atom and contains at least one hereto atom (O, S, N, Se, or Te) and may or may not contain C (9/547; 9/6524) {9}
90  DF  .~.~ Single N as only hetero atom in ring (9/553; 9/568) {6}
106.~.~.~ Four-membered ring containing a single N atom is condensed or bridged to a carbocyclic ring system (9/568V)

DEFINITION

Classification: 987/106

Four-membered ring containing a single N atom is condensed or bridged to a carbocyclic ring system (9/568V):

(under subclass 90) Subject matter wherein the ring which contains three carbons and a single nitrogen atom shares at least two of its ring carbons with a ring system containing only carbon atoms.